Shapechanger. The imp can use its action to polymorph into a beast form that resembles a rat (speed 20 ft.), a raven (20 ft., fly 60 ft.), or a spider (20 ft., climb 20 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.
Devil's Sight. Magical darkness doesn't impede the imp's darkvision.
Magic Resistance.The imp has advantage on saving throws against spells and other magical effects.
Poison Ennsnare
Once a week, Enn can provide a vial of poison from his stinger. Each vial contains 1 use. Targets afflicted with this poison must make a DC 11 Constitution saving throw, taking the poison damage on a failed save, or half as much damage on a successful one. The poison does (3d6) poison damage.
Sting (Bite in Beast Form). Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: (1d4 + 3) piercing damage plus (3d6)poison damage. The target must make a DC 11 Constitution saving throw, taking the poison damage on a failed save, or half as much damage on a successful one.
Invisibility. The imp magically turns invisible until it attacks, or until its concentration ends (as if concentrating on a spell). Any equipment the imp wears or carries is invisible with it.
Dragon's Beath
Choose acid, cold, fire, lightning, or poison. Until the spell ends, the creature can use an action to exhale energy of the chosen type in a 15-foot cone.
Each creature in that area must make a Dexterity saving throw, taking 3d6 damage of the chosen type on a failed save, or half as much damage on a successful one.