Geryon

If Geryon fails a saving throw, he can choose to succeed instead.

Geryon has advantage on saving throws against spells and other magical effects.

Geryon regains 20 hit points at the start of his turn. If he takes Radiant damage, this trait doesn't function at the start of his next turn. Geryon dies only if he starts his turn with 0 hit points and doesn't regenerate.

Geryon makes one Claw attack and one Stinger attack.

Melee Weapon Attack +16 to hit, reach 15 ft., one target. 23 (4d6 + 9) Cold damage. If the target is Large or smaller, it is Grappled (DC 24), and it is Restrained until the grapple ends. Geryon can grapple one creature at a time. If the target is already Grappled by Geryon, the target takes an extra 27 (6d8) Cold damage.

Melee Weapon Attack +16 to hit, reach 20 ft., one creature. 14 (2d4 + 9) Force damage, and the target must succeed on a DC 21 Constitution saving throw or take 13 (2d12) Poison damage and become Poisoned until it finishes a short or long rest. The target's hit point maximum is reduced by an amount equal to half the Poison damage taken. This reduction lasts until the Poisoned condition is removed. The target dies if its hit point maximum is reduced to 0.

Geryon teleports, along with any equipment he is wearing and carrying, up to 120 feet to an unoccupied space he can see.

Geryon targets one creature he can see within 60 feet of him. The target must succeed on a DC 23 Wisdom saving throw or become Frightened of Geryon until the end of its next turn.

Geryon uses Teleport.

Geryon makes one Stinger attack.