Unkindness of Ink-Ravens

Swarm. The swarm can occupy another creature's space and vice versa, and the swarm can move through any opening large enough for a Tiny raven. The swarm can't regain hit points or gain temporary hit points.

Flyby. The swarm doesn't provoke opportunity attacks when it flies out of an enemy's reach.

Limited Perception. The swarm does not have it's own independant perception and uses the line of sight and darkness limitations of it's summoner.

Crowd of Individuals. Six Ink-Ravens, each with 4 hit points (max HP/6), make up this swarm when it is summoned. As the swarm loses health the number of Ink-Ravens is reduced, as are the corresponding number of damage die used during any attack.

Nevermore. Regardless of whether they hit or not, the Ink-Ravens force a concentration check on any creature they share a space with (at the start of the concentrating creatures turn; multiple concentration checks can be triggered per turn).

Beaks. Melee Weapon Attack: +4 to hit, no reach, one target in the swarm's space. Hit: 3 (1d4) piercing damage per Ink-Raven in the swarm.

Viscious Opportunity Attack. The swarm makes an opportunity attack when a hostile creature: enters it's space, attempts leaves it's space, or casts a spell while sharing space with the swarm.

The Ink-Ravens only have one reaction per turn.