Born to Darkness. Magical darkness doesn't impede the spawn's darkvision.

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

Limited Telepathy. The Yog-spawn can magically communicate simple ideas, emotions, and images telepathically with any creature within 100 feet of it that can understand a language.

Tentacles. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 5 (1d4 + 3) bludgeoning damage, and the target must succeed on a DC 11 Wisdom saving throw, taking 10 (3d6) psychic 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.

Whispers from the Far Realm (1/day). One creature of the Yog-spawn's choice within 20 ft. of it must succeed on a DC 10 Wisdom saving throw or suffer a random effect from the madness table below for 1 minute. At the end of each of its turns, an affected target can make a wisdom saving throw. If it succeeds, this effect ends for that target.