Shapechanger. Zarkhul can use their bonus action to polymorph into a beast form that resembles a bat (speed 10 ft. fly 40 ft.), a centipede (40 ft., climb 40 ft.), or a toad (40 ft., swim 40 ft.), or back into its true form. Its statistics are the same in each form, except for the speed changes noted. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

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

Summon. Summons 2 weakened Dretches, or 3 weakened Manes, to its service from the Abyss, these creatures have half the HP and slightly weakened attacks as compared to the standard version of these creatures.

Claws (Bite in Beast Form). Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 5 (1d4 + 3) piercing damage, and the target must succeed on a DC 10 Constitution saving throw or take 5 (2d4) poison damage and become poisoned for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Scare (1/Day). One creature of Zarkhul's choice within 20 feet of it must succeed on a DC 10 Wisdom saving throw or be frightened for 1 minute. The target can repeat the saving throw at the end of each of its turns, with disadvantage if Zarkhul is within line of sight, ending the effect on itself on a success.

Invisibility. Zarkhul magically turns invisible until it attacks or uses Scare, or until its concentration ends (as if concentrating on a spell). Any equipment Zarkhul is wearing or carrying is invisible with it.

Flame. Zarkhul can summon a 15x15 ft square (3x3 tiles) of hellfire, centered around any point within the creature's view. Creatures within range, as well as creatures that move through it, must make a con saving throw, if they pass damage is halved, else they take full damage. 3d6 fire damage, ignores resistance and reduces immunities to resistances. These unholy flames last 1 minute, and creatures who take damage are set aflame and must make a dex saving throw to extinguish these flames at the start of each turn, creatures aflame take 1d6 damage every turn they are on fire.