Swarm of Vermin

The swarm has Advantage on an attack roll against a creature if at least one of the swarm's allies is within 5 feet of the creature and the ally doesn't have the Incapacitated condition.

The swarm can enter and occupy the space of another creature and vice versa, and the swarm can move through any opening large enough for a Tiny Beast.

Melee Attack Roll: Bonus equals your spell attack modifier, reach 0 ft. Hit: 2d6 + 1 + summonSpellLevel Piercing damage.