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.
Sting. Melee Attack Roll: +5, reach 5 ft. Hit: 1d6+3 Piercing damage plus 2d6 Poison damage. Change Shape. The imp changes into a form that resembles a rat (Speed 20 ft.), a raven (20 ft., Fly 60 ft.), or a spider (20 ft., Climb 20 ft.), or it returns to its true form. Its statistics are the same in each form, except for its Speed. Any equipment it's wearing or carrying isn't transformed. The imp reverts to its true form if it dies. Invisibility. The imp casts Invisibility on itself, requiring no spell components and using Charisma as the spellcasting ability.
Forest, Urban