Tiny undead, neutral evil
Armor Class 13
Hit Points 40 (9d4 + 18)
Speed 0 ft., fly 40 ft. (hover)
1 (-5)
17 (+3)
14 (+2)
16 (+3)
10 (+0)
11 (+0)
Skills Arcana +5, Perception +2
Damage Resistances lightning, necrotic, piercing
Damage Immunities cold, fire, poison
Condition Immunities charmed, frightened, paralyzed, poisoned, prone
Senses darkvision 60 ft., passive Perception 12
Languages Common
Challenge 4 (1100 XP)

Illumination. The flameskull sheds either dim light in a 15-foot radius, or bright light in a 15-foot radius and dim light for an additional 15 feet. It can switch between the options as an action.

Magic Resistance. The flameskull has advantage on saving throws against spells and other magical effects.

Rejuvenation. If the flameskull is destroyed, it regains all its hit points in 1 hour unless holy water is sprinkled on its remains or a dispel magic or remove curse spell is cast on them.

Spellcasting. The flameskull is a 5th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 13, +5 to hit with spell attacks). It requires no somatic or material components to cast its spells. The flameskull has the following wizard spells prepared:

Cantrips (at will): mage hand
1st level (3 slots): magic missile, shield
2nd level (2 slots): blur, flaming sphere
3rd level (1 slot): fireball

Multiattack. The flameskull uses Fire Ray twice.

Fire Ray. Ranged Spell Attack: +5 to hit, range 30 ft., one target. Hit: 10 (3d6) fire damage.

Blazing green flames and mad, echoing laughter surround an undead flameskull. This disembodied skull blasts foes with fiery rays from its eyes and dreadful spells called up from the dark recesses of its memory.
Monster Manual (BR)