Behydra

Hold Breath. The behydra can hold its breath for 1 hour.

Multiple Heads. The behydra has five heads. While it has more than one head, the behydra has advantage on saving throws against being blinded, charmed, deafened, frightened, stunned, and knocked unconscious.

Whenever the behydra takes 25 or more damage in a single turn, one of its heads dies. If all its heads die, the behydra dies.

At the end of its turn, it grows two heads for each of its heads that died since its last turn, unless it has taken fire damage since its last turn. The behydra regains 10 hit points for each head regrown in this way.

Reactive Heads. For each head the behydra has beyond one, it gets an extra reaction that can be used only for opportunity attacks.

Wakeful. While the behydra sleeps, at least one of its heads is awake.

Antimagic Cone. The behydra central eye creates an area of antimagic, as in the [Tooltip Not Found] spell, in a 150-foot-cone. At the start of each of its turns, the behydra decides which way the cone faces and whether the cone is active. The area works against the behydra's own eye rays.

Multiattack. The behydra makes as many bite attacks as it has heads. It can replace up to 3 of its bite attacks with Eye Rays. 

Bite. Melee Weapon Attack: + to hit, reach 10 ft., one target. Hit: 10 (1d10 + 10) piercing damage.

Eye Rays. The behydra shoots three of the following magical eye rays at random (reroll duplicates), choosing one to three targets it can see within 120 feet of it:

1. Charm Ray. The targeted creature must succeed on a DC 16 Wisdom saving throw or be charmed by the beholder for 1 hour, or until the beholder harms the creature.
2. Paralyzing Ray. The targeted creature must succeed on a DC 16 Constitution saving throw or be paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
3. Fear Ray. The targeted creature must succeed on a DC 16 Wisdom saving throw or be frightened for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
4. Slowing Ray. The targeted creature must succeed on a DC 16 Dexterity saving throw. On a failed save, the target’s speed is halved for 1 minute. In addition, the creature can’t take reactions, and it can take either an action or a bonus action on its turn, not both. The creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
5. Enervation Ray. The targeted creature must make a DC 16 Constitution saving throw, taking 36 (8d8) necrotic damage on a failed save, or half as much damage on a successful one.
6. Telekinetic Ray. If the target is a creature, it must succeed on a DC 16 Strength saving throw or the behydra moves it up to 30 feet in any direction. It is restrained by the ray’s telekinetic grip until the start of the behydra's next turn or until the behydra is incapacitated
   If the target is an object weighing 300 pounds or less that isn’t being worn or carried, it is moved up to 30 feet in any direction. The behydra can also exert fine control on objects with this ray, such as manipulating a simple tool or opening a door or a container.
7. Sleep Ray. The targeted creature must succeed on a DC 16 Wisdom saving throw or fall asleep and remain unconscious for 1 minute. The target awakens if it takes damage or another creature takes an action to wake it. This ray has no effect on constructs and undead.
8. Petrification Ray. The targeted creature must make a DC 16 Dexterity saving throw. On a failed save, the creature begins to turn to stone and is restrained. It must repeat the saving throw at the end of its next turn. On a success, the effect ends. On a failure, the creature is petrified until freed by the greater restoration spell or other magic.
9. Disintegration Ray. If the target is a creature, it must succeed on a DC 16 Dexterity saving throw or take 45 (10d8) force damage. If this damage reduces the creature to 0 hit points, its body becomes a pile of fine gray dust. If the target is a Large or smaller nonmagical object or creation of magical force, it is disintegrated without a saving throw. If the target is a Huge or larger object or creation of magical force, this ray disintegrates a 10-foot cube of it.
10. Death Ray. The targeted creature must succeed on a DC 16 Dexterity saving throw or take 55 (10d10) necrotic damage. The target dies if the ray reduces it to 0 hit points.

The behydra can take 3 legendary actions, using the Eye Ray option below. It can take only one legendary action at a time and only at the end of another creature’s turn. The behydra regains spent legendary actions at the start of its turn.

Eye Ray. The behydra uses one random eye ray.