Avoidance. If the cucco is subjected to an effect that allows it to make a saving throw to only take half damage, it instead takes no damage if it succeeds on the saving throw, and only half damage if it fails.
Gliding Flight. At beginning of each round as the cucco is flying, it falls 5 feet. If the cucco is lifting more than its carrying capacity (105,000 pounds), but not more than it can lift (210,000 pounds), it falls 15 feet per round instead. If the cucco is attempting to carry more weight than it can lift, it falls 60 feet per round, similar to feather fall. The cucco will drop anything heavier than 420,000 pounds. The cucco cannot gain height with its flight unless it is carrying nothing.
Legendary Resistance (5/Day). If the cucco fails a saving throw, it can choose to succeed instead.
Limited Magic Immunity. The cucco can't be affected or detected by spells of 4th level or lower unless it wishes to be. It has advantage on saving throws against all other spells and magical effects.
Magic Weapons. The cucco's weapon attacks are magical.
Pack Tactics. The cucco has advantage on an attack roll against a creature if at least one of the cucco's allies is within 5 feet of the creature and the ally isn't incapacitated.
Overpowered as Hell. The cucco can take one reaction per turn, rather than only one per round. It also has advantage on saving throws against being knocked unconscious. If it fails a saving throw against an effect that would stun a creature, one of its unspent legendary actions is spent.
Siege Monster. The cucco deals double damage to objects and structures.
Unyielding Essence. The cucco is immune to any spell or effect that would alter its form, as well as those that would read its thoughts, determine if it is lying, or magically influence its thoughts or behavior.
Peck. Melee Weapon Attack: automatic hit, reach 5 ft., one target. Hit: 30 (10d4 + 20) piercing damage.
Description
Not many a fowl is so prolific in the Material Plane as the humble cucco. Apparently, they were originally from the Far Realm, but these birds have spread far and wide throughout most of Wildspace. They are most commonly found in farms, ranches, and small settlements. People usually raise cuccos for the hearty eggs they produce, although plenty of individuals simply keep them as pets.
Surprisingly Strong. Cuccos are remarkably powerful for their small frame, able to carry more than a hundred thousand pounds, even if only temporarily. No one is quite sure how they manage this.
Vengeful Flock. Cuccos live in large family groups known as flocks. While normally harmless, peaceful and cowardly, they can quickly become dangerous in great numbers. If a cucco is under attack by a predator, it will call out to its feathery brethren to attack the assailant. As if from nowhere, dozens of cuccos will appear and descend on the unlucky foe.