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 abyssal chicken. The swarm can’t regain hit points or gain temporary hit points. It has a number of other traits described below.

Swarm Health. The swarm contains a number of abyssal chickens equal to its hit point total divided by 10. At full health, this is 216 chickens. For every 10 hit points the swarm loses, one chicken is killed, and conversely if a chicken dies the swarm loses 10 hit points. The swarm retains hit points from chickens that have been separated from it, as it has the ability to reform itself.

Swarm Dimensions. The swarm can occupy any number of 5-foot cubic spaces, so long as the number of abyssal chickens per space is between 5 and 8, rounded up. At full health, it commonly occupies a 15ft foot cube of 8 chickens per 5 foot space, or a 50ft by 100ft area on the ground at 5 chickens per space. The easiest way to track the density of its chickens is to divide the swarm's current hit points by ten times the number of spaces it occupies. At the end of every turn in combat, if the swarm has been separated into non-adjacent spaces or its density has fallen below 5, its Chaotic Coordination trait activates.

Chaotic Coordination. When this trait activates, the swarm adjusts its dimensions to raise its density back up to a value between 5 and 8, rounded up. The swarm can contract up to its movement in any direction, closing gaps and ignoring obstacles or difficult terrain. This movement provokes opportunity attacks as normal. It cannot use this trait to expand into unoccupied spaces, even if it could do so without lowering its density below the minimum threshold. It can use this trait to merge two smaller swarms into one larger contiguous swarm.

Area Damage Susceptibility. When a space the swarm occupies is subjected to an effect that deals 10 or more area damage, the swarm instead takes damage equal to 10 times the number of abyssal chickens in that area as all of the chickens die. Those spaces are temporarily unoccupied by the swarm until its Chaotic Coordination trait activates at the end of the turn.

Bad Fliers. The swarm can't occupy a space that is more than 15 feet off the ground, and it can't cross a horizontal chasm or clear a vertical surface larger than its movement speed.

Storm of Beak and Talon. Any creature that starts its turn within the swarm's area or enters it for the first time that turn takes damage from a flurry of demonic pecks and slashes. Refer to the Swarm Damage table below to determine how many d4's to roll. This number is based on the target's AC, the swarm's density, and the target's size. This damage is a combination of nonmagical piercing and slashing. If a target modifies the damage of one type but not the other, as with resistance or vulnerability, it applies to half of the damage dealt.

Chicken Run. The swarm enters a mad frenzy, doubling its movement speed until the start of its next turn. While this ability is active, its Storm of Beak and Talon trait can't activate.

Devour. All creatures in a space occupied by the swarm take damage from its Storm of Beak and Talon trait. This action can't be used if more than half of the spaces the swarm occupies are also occupied by other creatures.

Ravenous Expansion. The swarm adjusts its size up to its movement speed in any dimensions, so long as its density doesn't fall below 5 abyssal chickens per space, rounded up (see Swarm Dimensions). It can use this ability on the same turn it uses Chicken Run.