Dark One's Own Luck (Recharges after a Short or Long Rest). When the warlock makes an ability check or saving throw, it can add a d10 to the roll. It can do this after the roll is made but before any of the roll's effects occur.
Multiattack. The warlock makes three Scimitar attacks.
Scimitar. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) slashing damage plus 14 (4d6) fire damage.
Hellfire. Green flame explodes in a 10-foot-radius sphere centered on a point within 120 feet of the warlock. Each creature in that area must make a DC 15 Dexterity saving throw, taking 16 (3d10) fire damage and 11 (2d10) necrotic damage on a failed save, or half as much damage on a successful one.
Spellcasting. The warlock casts one of the following spells, using Charisma as the spellcasting ability (spell save DC 15):
At will: alter self, mage armor (self only), mage hand, minor illusion, prestidigitationFiendish Rebuke (3/Day). In response to being damaged by a visible creature within 60 feet of it, the warlock forces that creature to make a DC 15 Constitution saving throw, taking 22 (4d10) necrotic damage on a failed save, or half as much damage on a successful one.