Shapechanger. The calavire can use its action to polymorph into a Tiny bat, a Tiny hawk or a Medium cloud of mist, or back into its true form.
While in bat form, the calavire can't speak, its walking speed is 5 feet, and it has a flying speed of 30 feet. Its statistics, other than its size and speed, are unchanged. Anything it is wearing transforms with it, but nothing it is carrying does. It reverts to its true form if it dies.
While in mist form, the calavire can't take any actions, speak, or manipulate objects. It is weightless, has a flying speed of 20 feet, can hover, and can enter a hostile creature's space and stop there. In addition, if air can pass through a space, the mist can do so without squeezing, and it can’t pass through water. It has advantage on Strength, Dexterity, and Constitution saving throws, and it is immune to all nonmagical damage.
While in hawk form, the calavire can't speak, its walking speed is 10 feet, and its fly speed is 60 feet. Its statistics, other than its size and speed, are unchanged. Anything it is wearing transforms with it, but nothing it is carrying does. It reverts to its true form if it dies.
Legendary Resistance (5/Day). If the calavire fails a saving throw, it can choose to succeed instead.
Misty Escape. When it drops to 0 hit points outside its resting place, the calavire transforms into a cloud of mist (as in the Shapechanger trait) instead of falling unconscious.
While it has 0 hit points in mist form, it can't revert to its calavire form, and it must reach its resting place, or sunlight within 2 hours or be destroyed. Once in its resting place, it reverts to its calavire form. It is then paralyzed until it regains at least 1 hit point. After spending 1 hour in its resting place with 0 hit points, it regains 1 hit point.
Regeneration. The calavire regains 40 hit points at the start of its turn if it has at least 1 hit point.
Spider Climb. The calavire can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.
Avian Attributes. The calavire grows wings from its back, giving it a flight speed equal to its walking speed.
The calavire can also grow talons from its hands or feet at will.
Imbued with Light and Darkness. The calavire has immunity to necrotic and radiant damage, and its hit point maximum cannot be reduced
Multiattack. (Calavire Form Only). The calavire makes four attacks, only one of which can be a bite attack, and only one of which can be a talon attack.
Unarmed Strike (Calavire Form Only). Melee Weapon Attack: +9 to hit, reach 5 ft., one creature. Hit: 8 (1d8 + 4) bludgeoning damage. Instead of dealing damage, the calavire can grapple the target (escape DC 18).
Talons. (Hawk or Calavire Form Only). Melee Weapon Attack: +9 to hit, reach 5 ft., one willing creature, or a creature that is grappled by the calavire, incapacitated, or restrained. Hit: 7 (1d6 + 4) piercing damage plus 10 (3d6) radiant damage, or if the target is a willing creature, the talons only deal 1 damage, and restore 3d6 hit points. The calavire loses hit points equal to the amount of healing done.
Bite. (Bat or Calavire Form Only). Melee Weapon Attack: +9 to hit, reach 5 ft., one willing creature, or a creature that is grappled by the calavire, incapacitated, or restrained. Hit: 7 (1d6 + 4) piercing damage plus 10 (3d6) necrotic damage. The target's hit point maximum is reduced by an amount equal to the necrotic damage taken, and the calavire regains hit points equal to that amount. The reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0. A humanoid slain in this way and then buried in the ground rises the following night as a calavire spawn under the calavire's control.
Charm. The calavire targets one humanoid it can see within 30 feet of it. If the target can see the calavire, the target must succeed on a DC 17 Wisdom saving throw against this magic or be charmed by the calavire. The charmed target regards the calavire as a trusted friend to be heeded and protected. Although the target isn't under the calavire's control, it takes the calavire's requests or actions in the most favorable way it can, and it is a willing target for the calavire's bite attack.
Each time the calavire or the calavire's companions do anything harmful to the target, it can repeat the saving throw, ending the effect on itself on a success. Otherwise, the effect lasts 24 hours or until the calavire is destroyed, is on a different plane of existence than the target, or takes a bonus action to end the effect.
Children of the Night (1/Day). The calavire magically calls 2d4 swarms of bats or rats (swarm of bats, swarm of rats), provided that the sun isn't up. While outdoors, the calavire can call 3d6 wolves (wolf) instead. The called creatures arrive in 1d4 rounds, acting as allies of the calavire and obeying its spoken commands. The beasts remain for 1 hour, until the calavire dies, or until the calavire dismisses them as a bonus action.
The calavire can take 5 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The calavire regains spent legendary actions at the start of its turn.
Move. The calavire moves up to its speed without provoking opportunity attacks.
Unarmed Strike. The calavire makes one unarmed strike.
Bite.(Costs 2 Actions). The calavire makes one bite attack.
Talons.(Costs 2 Actions). The calavire makes one talon attack.