Basilisk Hivequeen

Petrifying Gaze. If a creature starts its turn within 30 feet of the basilisk and the two of them can see each other, the basilisk can force the creature to make a DC 20 Constitution saving throw if the basilisk isn't incapacitated. On a failed save, the creature magically 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.

A creature that isn't surprised can avert its eyes to avoid the saving throw at the start of its turn. If it does so, it can't see the basilisk until the start of its next turn, when it can avert its eyes again.

If it looks at the basilisk in the meantime, it must immediately make the save.

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

If the hivequeen takes more than 50 damage in a single round, one of its heads dies. If all of its heads die, the hivequeen does not die, but cannot use its Petrifying Gaze until it has at least one head.

Regeneration. At the beginning of its turn, the hivequeen regenerates. It regains 75 hitpoints and regenerates any heads it has lost, regaining an additional 10 hitpoints for each regenerated head. This trait does not function if the hivequeen has taken acid damage since its last turn.

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

Hivemind. Basilisk hiveminds share a single consciousness, controlled and manipulated by their Basilisk Hivequeen, who is rarely far away. As long as the Hivequeen is alive, all basilisks in the hive have advantage on saving throws against being magically put to sleep, they are immune to any spell effect that would compel them to act, and they cannot be charmed or frightened.

Immutable Form. The hivequeen is immune to any effect that would change its size or shape.

Multiattack. If the hivequeen starts its turn with at least one head, it uses its Compelling Roar, if it can. Then it bites with each of its heads.

Bite. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 20 (2d12 + 7) piercing damage and 27 (7d6) poison damage.

Queen’s Compelling Roar (Recharge 5-6). The hivequeen roars psychically, compelling every creature hostile to it within 60 feet to make eye contact. Each affected creature must make a DC15 Wisdom saving throw or be forced to attempt to make eye contact with the basilisk. A creature who is already compelled by another hivemind basilisk or a basilisk hivequeen automatically succeeds on the save. The hivequeen then chooses as many targets as it has heads that fail the save and locks eyes, subjecting them to its Petrifying Gaze (immediately, rather than on the creature’s turn).

The hivequeen can take three legendary actions, choosing from the list below. Each action must be taken at the end of another creature’s turn. She regains all spent legendary actions at the start of her turn.

Psionic Blast (3 actions). The hivequeen shrieks psychically. Each creature within 120 feet that is not part of her hivemind must succeed on a DC 18 Wisdom saving throw or take 21 (6d6) psychic damage. A creature who fails by more than 5 is stunned for 1 minute, or until the condition is removed with greater restoration or similar magic.

Bite. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 20 (2d12 + 7) piercing damage and 27 (7d6) poison damage.