Charybdis

Hideous. The first time a creature sees the Charybdis, it must succeed on a Wisdom (DC 16) saving throw or be frightened for 1 round.

Multi-Attack. The Charybdis can make two Bite attacks, one Whirlpool attack, or one Tsunami attack each turn.

Bite. Melee Weapon Attack: +4 to hit, reach 20 ft., 2 targets. Hit:  49 (6d12 + 10) piercing damage. If a Large or smaller target is hit twice in one round with the Bite attack, the target is Swallowed (See below).

Whirlpool. Melee Weapon Attack: reach 100 ft., all targets in range. Each target in range must make a Strength (DC 18) saving throw. Targets take 2d10 + 10 bludgeoning damage and are Swallowed (See below) on a failed safe, or half as much damage and are not Swallowed on a successful one.

Water Pulse. The Charybdis releases a strong pulse of water that ripples under the surface. Any object, including creatures, within a 100 ft. long, 25 ft. wide line must make a DC 18 Dexterity saving throw. On a failed save the object takes 30 (6d8+3) force damage and is pushed back a number of feet equal to the amount of damage they took. On a successful save, the object takes half the damage and is pushed back half by a number of feet equal to half the amount of damage taken. Inanimate objects automatically fail the save.

When a target is Swallowed by the Charybdis, it is blinded and deafened and has immunity to all attacks outside of the Charybdis. At the beginning of each of the Charybdis' turns, every creature Swallowed by the Charybdis must make a Constitution (DC 18) saving throw. Targets take 6d6 bludgeoning damage on a failed save, or half as much on a successful one. If the damage dealt to the Charybdis (from the inside and outside) exceeds 60 points, the Charybdis needs to make a Constitution (DC 21) saving throw or expel all Swallowed targets, who exit prone 10 feet away. If the Charybdis dies with a target inside of it, the target can spend 20 feet of movement to escape and they exit prone 5 feet away. There is no limit to the number of targets the Charybdis can hold.

The Charybdis has 3 Legendary Actions that it can use after it has been attacked. It regains all expended Legendary Actions every turn.

Bite (Costs 1 Action). The Charybdis makes a Bite attack at the target that attacked it. This does not count to the count needed to swallow the target.

Water Pulse (Costs 3 Actions). The Charybdis uses the Water Pulse attack on its next turn (It makes a Water Pulse attack in addition to its other attacks).