Telepathic Bond. The fiend ignores the range restriction on its telepathy when communicating with a creature it has charmed. The two don't even need to be on the same plane of existence.

Planar Chains. When Xolofompilas deals damage to a creature, the warlock who summoned it gains advantage on the next attack they make on their following turn. However, the warlock suffers a –1 penalty to Charisma checks made outside of combat for 24 hours (stacking up to –3).

Ritual Pain Whip. Melee Spell Attack: +8 to hit, reach 5 ft.
Hit: 3d8 +5 necrotic damage. The target must make a DC 16 Wisdom saving throw: Failure: The target is frightened until the end of its next turn. Success: The target only feels a chilling, rending shiver.

Mind Shard (Recharge 5–6). One creature within 60 ft. must make a DC 16 Intelligence saving throw. Failure: 4d6 psychic damage and the target is stunned until the start of Xol'ofompilas’s next turn. Success: Half damage and no stunned condition.

Silent Scream (1/day). Xol'ofompilas “opens its mouth,” yet no sound escapes — but everyone feels it. Each creature within 20 ft. must make a DC 16 Constitution saving throw. Failure: The creature is deafened for 1 minute and takes 3d6 psychic damage. Success: Half damage.