Prerequisite: Swarm subclass, Warlock level 6

While in swarm form you can speak telepathically with a creature sharing your space, and your swarm attack can deal psychic damage rather than piercing. Additionally, you gain the following ability.

Terrifying Visions. While in swarm form, you can use an action to force a creature in your space to make a Wisdom saving throw. On a failure, that creature is frightened for 1 minute or until you lose concentration, as if on a spell. The frightened target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. Constructs and undead are unaffected by this ability. Once you have used this action, you cannot use it again until you've had a short rest.