Sage Advice : Spellcasting
Can a spellcaster cast spells off-target to minimize damage to party members from a spell like shatter?
The spellcaster chooses where to place the point of origin of a spell like shatter and may, therefore, choose a position that is advantageous to allies.
Can permanent magical effects be dispelled? Or are they no longer considered magical effects once permanent?
If the effect of a spell becomes permanent, it can be dispelled, unless its description says otherwise (such as in the wall of stone spell.
Do spellcasters have to learn a ritual version of a spell apart from the normal version, or are they the same?
To cast the ritual version of a spell you know, you need a feature, such as Ritual Casting, that gives you the ability to cast the spell as a ritual. You don’t need to also learn a special version of the spell.
Can spellcasters prepare spells not all at once, but prepare spells at various times in the day?
You prepare your list of spells only at the end of a long rest. You can’t prepare some spells at the end of the rest and then prepare more later.
Do you always know when you’re under the effect of a spell?
You’re aware that a spell is affecting you if it has a perceptible effect or if its text says you’re aware of it (see PH, 204, under "Targets"). Most spells are obvious. For example, fireball burns you, cure wounds heals you, and command forces you to suddenly do something you didn’t intend. Certain spells are more subtle, yet you become aware of the spell at a time specified in the spell’s description. Charm person and detect thoughts are examples of such spells.
Some spells are so subtle that you might not know you were ever under their effects. A prime example of that sort of spell is suggestion. Assuming you failed to notice the spellcaster casting the spell, you might simply remember the caster saying, "The treasure you’re looking for isn’t here. Go look for it in the room at the top of the next tower." You failed your saving throw, and off you went to the other tower, thinking it was your idea to go there. You and your companions might deduce that you were beguiled if evidence of the spell is found. It’s ultimately up to the DM whether you discover the presence of inconspicuous spells. Discovery usually comes through the use of skills like Arcana, Investigation, Insight, and Perception or through spells like detect magic.
Is a touch range spell considered a melee attack for purposes of subduing foes rather than killing?
Having a range of touch doesn’t mean a spell is a melee attack. A spell tells you if it delivers such an attack.
Can spell attacks score critical hits?
A spell attack can definitely score a critical hit. The rule on critical hits applies to attack rolls of any sort.
When casting a spell that affects multiple targets, such as scorching ray or eldritch blast, do I fire one ray or beam, determine the result, and fire again? Or do I have to choose all the targets before making any attack rolls?
Even though the duration of each of these spells is instantaneous, you choose the targets and resolve the attacks consecutively, not all at once. If you want, you can declare all your targets before making any attacks, but you would still roll separately for each attack (and damage, if appropriate).
Can a spell with an attack roll be used as the attack in the Attack action or as part of the Extra Attack feature?
The short answer is no.
As explained in the Player’s Handbook, you can take one action on your turn in combat, in addition to moving. You choose your action from the options available to everyone— options such as Attack, Cast a Spell, and Dash—or you choose from among the special actions you’ve gained from a class, a feat, or another source. If you want to cast a spell on your turn, you take the Cast a Spell action. Doing so means you’re not taking the Attack action or any other action. It is true that a number of spells, such as fire bolt and ray of frost, involve making an attack, but you can’t make such an attack without first casting the spell that delivers it. In other words, just because something involves an attack doesn’t mean the Attack action is being used. By extension, the Extra Attack feature (given by several classes, including the fighter and paladin) doesn’t let you cast extra attack spells. That feature specifically relies on the Attack action, not the Cast a Spell action or any other action.
In summary, to make a spell attack, you have to first cast a spell or use a feature that creates the spell’s effect. A game feature, such as Extra Attack, that lets you make an attack doesn’t let you cast a spell unless it says it does.
Can you use a melee spell attack to make an opportunity attack?
You can’t if the spell attack is created by casting a spell. When a creature triggers an opportunity attack from you, you can use your reaction to make a melee attack against it. The opportunity attack doesn’t suddenly give you the ability to cast a spell, such as shocking grasp. Each spell has a casting time. A game feature, such as an opportunity attack, doesn’t let you bypass that casting time, unless the feature says otherwise. The War Caster feat is an example of a feature that does let you bypass a 1-action casting time to cast a spell in place of making an opportunity attack.
A few monsters can make opportunity attacks with melee spell attacks. Here’s how: certain monsters—including the banshee, the lich, and the specter—have a melee spell attack that isn’t delivered by a spell. For example, the banshee’s Corrupting Touch action is a melee spell attack but no spell is cast to make it. The banshee can, therefore, make opportunity attacks with Corrupting Touch.
Some spells (like eldritch blast) target a creature. Some others (like fire bolt) target objects too. Does this mean that I can’t attack the door with eldritch blast?
The target specifications (creature, object, or something else) in spells are intentional.
Does a melee spell attack count as a melee attack for Touch of Death?
A melee spell attack is, indeed, a melee attack and can qualify for the Death cleric’s Touch of Death feature.
What level is a spell if you cast it without a spell slot?
Such a spell is cast at its lowest possible level, which is the level that appears near the top of its description. Unless you have a special ability that says otherwise, the only way to increase the level of a spell is to expend a higher-level spell slot when you cast it. Here are some examples:
- The warlock’s Chains of Carceri feature lets a warlock cast hold monster without using a spell slot. That casting of hold monster is, therefore, 5th level, which is the lowest possible level for that spell.
- The warlock’s Thief of Five Fates feature lets a warlock cast bane using a spell slot, which means the spell is 1st level or higher, depending on the slot that the warlock expends to cast it.
- The monk’s Disciple of the Elements feature lets the monk spend ki points, rather than a spell slot, to increase the level of a spell.
This rule is true for player characters and monsters alike, which is why the innate spellcasters in the Monster Manual must cast an innate spell at its lowest possible level.
If a character has levels in more than one class, do the character’s cantrips scale with character level or with the level in a spellcasting class?
Cantrips scale with character level. For example, a barbarian 2 / cleric 3 casts sacred flame as a 5th-level character.
Is there a limit on the number of spells you can cast on your turn?
There’s no rule that says you can cast only X number of spells on your turn, but there are some practical limits. The main limiting factor is your action. Most spells require an action to cast, and unless you use a feature like the fighter’s Action Surge, you have only one action on your turn.
If you cast a spell, such as healing word, with a bonus action, you can cast another spell with your action, but that other spell must be a cantrip. Keep in mind that this particular limit is specific to spells that use a bonus action. For instance, if you cast a second spell using Action Surge, you aren’t limited to casting a cantrip with it.
Does the rule on casting a bonus action spell apply when you take a bonus action granted by a spell?
The rule on casting a spell as a bonus action (see PH, 202) applies only on the turn you cast the spell. For example, spiritual weapon can be cast as a bonus action, and it lasts for 1 minute. On the turn you cast it, you can’t cast another spell before or after it, unless that spell is a cantrip with a casting time of 1 action. Until spiritual weapon ends, it gives you the option of controlling its spectral weapon as a bonus action. That bonus action does not involve casting a spell, despite the fact that it’s granted by a spell, so you can control the weapon and cast whatever spell you like on the same turn.
Can you cast a reaction spell on your turn?
You sure can! Here’s a common way for it to happen: Cornelius the wizard is casting fireball on his turn, and his foe casts counterspell on him. Cornelius also has counterspell prepared, so he uses his reaction to cast it and break his foe’s counterspell before it can stop fireball.
Does casting a spell as a ritual require concentration if the spell doesn’t normally require it?
Concentration is required when casting any spell, including a ritual version, for longer than 1 action (see PH, 202). Once the casting is complete, the spell requires concentration only if its duration entry says it does.
Does a spell consume its material components?
A spell doesn’t consume its material components unless its description says it does. For example, the pearl required by the identify spell isn’t consumed, whereas the diamond required by raise dead is used up when you cast the spell.
If a spell’s material components are consumed, can a spellcasting focus still be used in place of the consumed component?
No. A spellcasting focus can be used in place of a material component only if that component has no cost noted in the spell’s description and if that component isn’t consumed.
What’s the amount of interaction needed to use a spellcasting focus? Does it have to be included in the somatic component?
If a spell has a material component, you need to handle that component when you cast the spell (PH, 203). The same rule applies if you’re using a spellcasting focus as the material component.
If a spell has a somatic component, you can use the hand that performs the somatic component to also handle the material component. For example, a wizard who uses an orb as a spellcasting focus could hold a quarterstaff in one hand and the orb in the other, and he could cast lightning bolt by using the orb as the spell’s material component and the orb hand to perform the spell’s somatic component. Another example: a cleric’s holy symbol is emblazoned on her shield. She likes to wade into melee combat with a mace in one hand and a shield in the other. She uses the holy symbol as her spellcasting focus, so she needs to have the shield in hand when she casts a cleric spell that has a material component. If the spell, such as aid, also has a somatic component, she can perform that component with the shield hand and keep holding the mace in the other. If the same cleric casts cure wounds, she needs to put the mace or the shield away, because that spell doesn’t have a material component but does have a somatic component. She’s going to need a free hand to make the spell’s gestures. If she had the War Caster feat, she could ignore this restriction.
If you’re concentrating on a spell, do you need to maintain line of sight with the spell’s target or the spell’s effect?
You don’t need to be within line of sight or within range to maintain concentration on a spell, unless a spell’s description or other game feature says otherwise.
If I have 10 temporary hit points and I take 30 damage from an attack while concentrating on a spell, what is the DC of the Constitution save to maintain my concentration?
The DC is 15 in that case. When temporary hit points absorb damage for you, you’re still taking damage, just not to your real hit points. In contrast, a feature like the wizard’s Arcane Ward can take damage for you, potentially eliminating the need to make a Constitution saving throw or, at least, lowering the DC of that save.
Can a spellcaster dismiss a spell after casting it?
You can’t normally dismiss a spell that you cast unless (a) its description says you can or (b) it requires concentration and you decide to end your concentration on it. Otherwise, a spell’s magic is unleashed on the environment, and if you want to end it, you need to cast dispel magic on it.
Can you extend the duration of armor of Agathys by gaining more temporary hit points?
The spell is meant to work only as long as you have the temporary hit points that the spell grants. When those temporary hit points are gone, the spell is done. Keep in mind that temporary hit points aren’t cumulative (see PH, 198). If you have temporary hit points and receive more of them, you don’t add them together, unless a game feature says you can. You decide which temporary hit points to keep. As an example, let’s say you’re a warlock with the Dark One’s Blessing feature, which gives you temporary hit points when you reduce a creature to 0 hit points. You currently have 2 temporary hit points remaining from armor of Agathys, you just slew a monster, and your Dark One’s Blessing can now give you 4 temporary hit points. If you take those temporary hit points, they replace the ones from armor of Agathys and end that spell, so you might not want to take them and keep the spell going instead, so as to continue benefiting from the cold damage it delivers.
How does barkskin work with shields, cover, and other modifiers to AC?
Barkskin specifies that your AC can’t be lower than 16 while you are affected by the spell. This means you effectively ignore any modifiers to your AC—including your Dexterity modifier, your armor, a shield, and cover—unless your AC is higher than 16. For example, if your AC is normally 14, it’s 16 while barkskin is on you. If your AC is normally 15 and you have half cover, your AC is 17; barkskin isn’t relevant in this case.
Does the blinding smite spell deal extra radiant damage on every successful attack I make while I’m concentrating on the spell, or only on the first one?
"The next time" in the spell description indicates that the extra damage applies only once, the first time you hit a creature after you finish casting the spell.
Is the chill touch spell intended as a way of foiling any creature that has Regeneration?
Chill touch does, indeed, stop the target it hits from regaining hit points until the spell ends. This is true even if the target takes none of the necrotic damage, whether because of immunity or some other reason.
Using 5-foot squares, does cloud of daggers affect a single square?
Cloud of daggers (5 ft. cube) can affect more than one square on a grid, unless the DM says effects snap to the grid. There are many ways to position that cube.
Is the damage dealt by a beast from conjure animals considered magical?
The stat block of a conjured creature determines the nature of the creature’s damage, unless the spell says otherwise.
When you cast a spell like conjure woodland beings, does the spellcaster or the DM choose the creatures that are conjured?
A number of spells in the game let you summon creatures. Conjure animals, conjure celestial, conjure minor elementals, and conjure woodland beings are just a few examples. Some spells of this sort specify that the spellcaster chooses the creature conjured. For example, find familiar gives the caster a list of animals to choose from. Other spells of this sort let the spellcaster choose from among several broad options. For example, conjure minor elementals offers four options. Here are the first two:
- One elemental of challenge rating 2 or lower
- Two elementals of challenge rating 1 or lower
The design intent for options like these is that the spellcaster chooses one of them, and then the DM decides what creatures appear that fit the chosen option. For example, if you pick the second option, the DM chooses the two elementals that have a challenge rating of 1 or lower. A spellcaster can certainly express a preference for what creatures shows up, but it’s up to the DM to determine if they do. The DM will often choose creatures that are appropriate for the campaign and that will be fun to introduce in a scene.
Do contagion effects kick in immediately, or do they kick in when the target fails the three saving throws?
The effects of the contagion spell’s disease activate after three failed saving throws. When the spell attack hits, it effectively infects the target with a magical disease that requires a little bit of time to take effect before plaguing the target for up to a week.
Can you cast darkness with a higher-level slot to end a spell of 3rd level or higher that creates light?
No. The darkness spell can dispel only a light-creating spell of 2nd level or lower, no matter what spell slot is used for darkness. Similarly, the daylight spell can dispel only a darkness-creating spell of 3rd level or lower, regardless of the spell slot used.
If the damage from disintegrate reduces a half-orc to 0 hit points, can Relentless Endurance prevent the orc from turning to ash?
Yes. The disintegrate spell turns you into dust only if the spell’s damage leaves you with 0 hit points. If you’re a half-orc, Relentless Endurance can turn the 0 into a 1 before the spell can disintegrate you.
What happens if a druid using Wild Shape is reduced to 0 hit points by disintegrate? Does the druid simply leave beast form?
The druid leaves beast form. As usual, any leftover damage then applies to the druid’s normal hit points. If the leftover damage leaves the druid with 0 hit points, the druid is disintegrated.
Can you use dispel magic to dispel a magical effect like a vampire’s Charm ability?
Dispel magic has a particular purpose: to break other spells. It has no effect on a vampire’s Charm ability or any other magical effect that isn’t a spell. It also does nothing to the properties of a magic item. It can, however, end a spell cast from a magic item or from another source. Spells—they’re what dispel magic is about. For example, if you cast dispel magic on a staff of power, the spell fails to disrupt the staff’s magical properties, but if the staff’s wielder casts hold monster from the staff, dispel magic can end that spell if cast on the target of hold monster. There are abilities and other spells that can end or suspend magical effects that aren’t spells. For example, the greater restoration spell can end a charm effect of any sort on a target (such as a vampire’s Charm or a dryad’s Fey Charm), and a paladin’s Aura of Devotion can prevent or suspend such an effect. Three of the most versatile spells for ending certain magical effects are lesser restoration, greater restoration, and remove curse.
Can you use dispel magic on the creations of a spell like animate dead or affect those creations with antimagic field?
Whenever you wonder whether a spell’s effects can be dispelled or suspended, you need to answer one question: is the spell’s duration instantaneous? If the answer is yes, there is nothing to dispel or suspend. Here’s why: the effects of an instantaneous spell are brought into being by magic, but the effects aren’t sustained by magic (see PH, 203). The magic flares for a split second and then vanishes. For example, the instantaneous spell animate dead harnesses magical energy to turn a corpse or a pile of bones into an undead creature. That necromantic magic is present for an instant and is then gone. The resulting undead now exists without the magic’s help. Casting dispel magic on the creature can’t end its mockery of life, and the undead can wander into an antimagic field with no adverse effect. Another example: cure wounds instantaneously restores hit points to a creature. Because the spell’s duration is instantaneous, the restoration can’t be later dispelled. And you don’t suddenly lose hit points if you step into an antimagic field! In contrast, a spell like conjure woodland beings has a non-instantaneous duration, which means its creations can be ended by dispel magic and they temporarily disappear within an antimagic field.
Can you ready dispel magic to stop another spell from taking effect?
The easiest way to stop a spell is to cast counterspell on its caster while it’s being cast. If successful, counterspell interrupts the other spell’s casting, and that spell fails to take effect. Counterspell works against any spell, regardless of a spell’s casting time or duration. With the Ready action, dispel magic can be cast in response to another spell being cast, yet dispel magic can’t substitute for counterspell. The main reason is that dispel magic removes a spell that is already on a target, whether that target is a creature, an object, or some other phenomenon. Dispel magic can’t dispel something in advance. If a spell isn’t already present on a target, dispel magic does nothing to that target. The best that a readied dispel magic can do is dispel a spell immediately after the spell has been cast to prevent it from having any effect after the action used to cast it. For example, on your turn you could say something like this: "I ready dispel magic, and if the high priest casts a spell on anyone, I cast dispel magic on the target if the spell takes hold." If the high priest then cast hold person on your companion who fails the save against it, you could unleash your readied dispel magic and end hold person.
Can dispel magic end globe of invulnerability?
Yes, dispel magic can dispel the barrier created by globe of invulnerability, but not any magical effects that are active inside the barrier.
If dispel magic targets the magical effect from bless cast by a cleric, does it remove the effect on all the targets?
Dispel magic ends a spell on one target. It doesn’t end the same spell on other targets.
Can the familiar you conjure with the find familiar spell use the Help action to grant you advantage on your attack roll?
A familiar can’t attack, but it can take non-attack actions, including Help. As the text of the Help action indicates (PH, 192), the action doesn’t require you to be able to attack; you simply need to be able to provide some sort of distraction.
Does the familiar of find familiar count as an ally for the purposes of Sneak Attack?
A familiar is an allied creature. Its proximity to a target can allow you to use the Sneak Attack feature or any other feature that requires the presence of an ally.
Can a spell such as fireball go past its 20-foot radius if the point of origin is set in an enclosed space that’s less than 40 feet across?
The fire of the fireball spell can spread around corners, but it’s limited by the spell’s 20-foot radius. It doesn’t extend farther than 20 feet from the point of origin no matter where it is cast.
If I’m a cleric/druid with the Disciple of Life feature, does the goodberry spell benefit from the feature?
Yes. The Disciple of Life feature would make each berry restore 4 hit points, instead of 1, assuming you cast goodberry with a 1st-level spell slot.
Can you use green-flame blade and booming blade with Extra Attack, opportunity attacks, Sneak Attack, and other weapon attack options?
Introduced in the Sword Coast Adventurer’s Guide, the green-flame blade and booming blade spells pose a number of questions, because they each do something unusual: require you to make a melee attack with a weapon as part of the spell’s casting.
First, each of these spells involves a normal melee weapon attack, not a spell attack, so you use whatever ability modifier you normally use with the weapon. (A spell tells you if it includes a spell attack, and neither of these spells do.) For example, if you use a longsword with green-flame blade, you use your Strength modifier for the weapon’s attack and damage rolls.
Second, neither green-flame blade nor booming blade works with Extra Attack or any other feature that requires the Attack action. Like other spells, these cantrips require the Cast a Spell action, not the Attack action, and they can’t be used to make an opportunity attack, unless a special feature allows you to do so.
Third, these weapon attacks work with Sneak Attack if they fulfill the normal requirements for that feature. For example, if you have the Sneak Attack feature and cast green-flame blade with a finesse weapon, you can deal Sneak Attack damage to the target of the weapon attack if you have advantage on the attack roll and hit.
For the spell hail of thorns, does it last for the initial attack or as long as you maintain concentration?
Hail of thorns lasts until you hit a creature with a ranged weapon attack or your concentration ends, whichever comes first.
Can the extra action granted by haste be used to activate a magic item?
No. Activating a magic item isn’t a function of the Use an Object action (DMG, 141).
Does the heroes’ feast spell grant immunity to poison damage or just the poison condition?
The heroes’ feast spell grants immunity to poison in any form—damage and the condition.
Do the temporary hit points from heroism accumulate each round?
Temporary hit points aren’t cumulative. The spell would tell you if you were meant to add together the temporary hit points it provides. At the start of each of your turns, the spell, effectively, refreshes the number of temporary hit points you have from it; if you lost some or all of the temporary hit points, the spell gives them back to you.
If the heroism spell is cast on a character that is already frightened, does it remove the frightened effect?
The heroism spell would suppress a frightening effect that was already on its target. When the spell ends, the target’s immunity goes away and the frightening effect resumes if it has not expired or been removed.
Does the extra damage from hex only apply if there is an attack roll?
The extra damage in the hex spell requires an attack that hits.
Since resting identifies magic items, and the identify spell doesn’t spot curses, what is the role of the identify spell?
The most important factors are time and convenience. During a short rest, which takes at least 1 hour, a character who meets the qualifications can determine the properties of one magic item (see "Identifying a Magic Item" on page 136 of the Dungeon Master’s Guide). In contrast, casting the identify spell takes only 1 minute (or 11 minutes if it is cast as a ritual) and can be done when a quick determination is needed.
What happens when a jump spell gives a creature a jump distance greater than its walking speed?
Your jump is limited by how far you can move; each foot jumped uses a foot of movement. You can take the Dash action if you want to extend how far you can move on your turn. For example, if you have a Strength score of 15, you can normally leap 15 feet when you make a long jump if you move at least 10 feet immediately beforehand. If the jump spell is cast on you, that potential jump distance is tripled. That’s a jump of 45 feet! If your speed is 30 feet, you can use only 30 feet of that jump distance on your turn, unless you take the Dash action, which allows you to leap the full 45 feet.
Can you use a shield with mage armor?
Mage armor works with a shield. Shields are grouped with armor in the equipment rules in the Player’s Handbook, but various game features distinguish between the armor you wear and a shield you wield. Take a look at the monk’s Unarmored Defense feature and compare it to the barbarian’s version. In the monk’s version, you must both forgo wearing armor and forgo wielding a shield if you want to benefit from the feature, whereas a barbarian must only forgo wearing armor.
Does Unarmored Defense work with a spell like mage armor?
Unarmored Defense doesn’t work with mage armor. You might be asking yourself, "Why don’t they work together? Mage armor specifies that it works on a creature who isn’t wearing armor." It’s true that the target of mage armor must be unarmored, but mage armor gives you a new way to calculate your AC (13 + your Dexterity modifier) and is therefore incompatible with Unarmored Defense or any other feature that provides an AC calculation.
I find it confusing that the mage armor spell is named that when it doesn’t count as armor.
Some spells and class features have figurative, not literal, names. The text of the spell or class feature explains what it does. In this case, mage armor (PH, 256) surrounds the target with "protective magical force"; the spell doesn’t provide armor.
Can an object created with minor illusion move? For example, a wall sliding down a corridor?
An illusory object created by minor illusion doesn’t move. Compare to spells like major image and mislead, which talk about moving.
Could minor illusion create a fog cloud? If so, would shooting an arrow through it cancel the illusion?
An illusory object made by minor illusion is meant to be like a stool or a rock, not an atmospheric effect.
Does moonbeam deal damage when you cast it? What about when its effect moves onto a creature?
The answer to both questions is no. Here’s some elaboration on that answer.
Some spells and other game features create an area of effect that does something when a creature enters that area for the first time on a turn or when a creature starts its turn in that area. On the turn when you cast such a spell, you’re primarily setting up hurt for your foes on later turns. Moonbeam, for example, creates a beam of light that can damage a creature who enters the beam or who starts its turn in the beam.
Here are some spells with the same timing as moonbeam for their areas of effect:
- blade barrier
- cloud of daggers
- Evard’s black tentacles
- sleet storm
- spirit guardians
Reading the description of any of those spells, you might wonder whether a creature is considered to be entering the spell’s area of effect if the area is created on the creature’s space. And if the area of effect can be moved—as the beam of moonbeam can—does moving it into a creature’s space count as the creature entering the area? Our design intent for such spells is this: a creature enters the area of effect when the creature passes into it. Creating the area of effect on the creature or moving it onto the creature doesn’t count. If the creature is still in the area at the start of its turn, it is subjected to the area’s effect.
Entering such an area of effect needn’t be voluntary, unless a spell says otherwise. You can, therefore, hurl a creature into the area with a spell like thunderwave. We consider that clever play, not an imbalance, so hurl away! Keep in mind, however, that a creature is subjected to such an area of effect only the first time it enters the area on a turn. You can’t move a creature in and out of it to damage it over and over again on the same turn.
In summary, a spell like moonbeam affects a creature when the creature passes into the spell’s area of effect and when the creature starts its turn there. You’re essentially creating a hazard on the battlefield.
Does planar binding summon the creature to be bound, or is that done separately?
Planar binding doesn’t summon a creature. It attempts to bind a creature that is within the spell’s range.
Can you concentrate on a spell while transformed by polymorph?
You can’t cast spells while you’re transformed by polymorph, but nothing in the spell prevents you from concentrating on a spell that you previously cast before being transformed.
Does a willing creature under the effects of polymorph have to take the mental stats of the new form?
Yes. Unless a spell tells you otherwise, its effect is no different for a willing creature than it is for an unwilling one.
What kinds of things count as "nonmagical trinkets" for prestidigitation?
Prestidigitation can create a little bauble, the nature of which is up to the spellcaster and the DM. See the Trinkets table in the Player’s Handbook (p. 160–61) for examples.
If you grapple or shove an enemy creature, does that end a sanctuary spell cast on you?
If you use the grapple or shove option in the combat rules (PH, 195), the sanctuary spell does end on you, since you have made an attack.
If I cast shillelagh on my quarterstaff and have the Polearm Master feat, does the bonus attack use a d4 or a d8 for damage?
The benefit from Polearm Master applies to the opposite end of the weapon and always uses a d4 for damage rather than the weapon’s normal damage die. This is true for a quarterstaff enhanced with shillelagh just as it is for a normal one.
The stinking cloud spell says that a creature wastes its action on a failed save. So can it still use a move or a bonus action or a reaction?
Correct. The gas doesn’t immobilize a creature or prevent it from acting altogether, but the effect of the spell does limit what it can accomplish while the cloud lingers.
Do the effects of storm of vengeance stack? Or do the effects change each turn?
In the spell storm of vengeance, each new effect replaces the effect of the previous round.
Is the sentence of suggestion in the suggestion spell the verbal component, or is the verbal component separate?
Verbal components are mystic words (PH, 203), not normal speech. The spell’s suggestion is an intelligible utterance that is separate from the verbal component. The command spell is the simplest example of this principle. The utterance of the verbal component is separate from, and precedes, any verbal utterance that would bring about the spell’s effect.
The wording in Tasha’s hideous laughter implies that the incapacitated effect applies only if the target is made prone. Is this right?
Failing a save against Tasha’s hideous laughter means you’re incapacitated even if you can’t fall prone.
Can I use unseen servant to act as an ally when using a class feature like Sneak Attack?
Unseen servant creates "an invisible, mindless, shapeless force" (PH, 284). In combat, it doesn’t act as a creature, an enemy, or an ally.
Whenever you cast wish, do you always have a 33 percent chance of never casting it again?
If you cast wish to duplicate a spell of level 0–8, there are no detrimental effects. However, if you do anything other than duplicate a spell of level 0–8, you suffer the stress described in the final paragraph of the spell. As soon as that stress affects you, there is a 33 percent chance that you are unable to cast wish again.
Written by Jeremy Crawford (Sage Advice Compendium v2.3)