Cervantas

Legendary Resistance (3/Day). If Cervantas fails a saving throw, it can choose to succeed instead.

Magic Resistance. Cervantas has advantage on saving throws against spells and other magical effects.

Siege Monster. Cervantas deals double damage to objects and structures.

Amphibious. Cervantas can breathe air and water.

Multiattack. Cervantas uses its frightful presence. It then makes three attacks: two with its claws and one with its tail. It can swap its tail attack for an Entangle or Swallow.

Claw. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 15 (2d8 + 6) piercing damage.

Tail. Melee Weapon Attack: +10 to hit, reach 25 ft., one target. Hit: 13 (2d6 + 6) bludgeoning damage.

Frightful Presence. Each creature of Cervantas's choice within 120 feet of it and aware of it must succeed on a DC 14 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, with disadvantage if Cervantas is within line of sight, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to Cervantas's Frightful Presence for the next 24 hours.

Entangle. Cervantas makes a tail attack against a Huge or smaller creature. On a hit, it is grappled (escape DC 18) and pulled into Cervantas's space. Until this grapple ends, the target is restrained. Cervantas can grapple up to one Huge creature, or a cumulative amount of smaller creatures equal to that size (two Large, four medium, etc).

Swallow. Melee Weapon Attack: +10 to hit, reach 0 ft., one Large or smaller creature that is grappled by Cervantas. Hit: The target is swallowed, and the grapple ends. While swallowed, the creature is blinded and restrained, it has total cover against attacks and other effects outside Cervantas, and it takes 42 (12d6) acid damage at the start of each of the Cervantas turns.

If Cervantas takes 25 damage or more on a single turn from a creature inside it, Cervantas must succeed on a DC 20 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of Cervantas. If Cervantas dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 30 feet of movement, exiting prone.

Cervantas can take 3 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. Cervantas regains spent legendary actions at the start of its turn.

Tail. Cervantas makes one tail attack.

Move. Cervantas moves up to half its movement speed.

Crush (Costs 2 Actions). Cervantas attempts to crush all creatures it currently has grappled by its Entangle attack. Each creature must make a DC 18 Strength saving throw or take 28 (8d6) bludgeoning damage on a failure.

Tangling Charge (Costs 3 Actions). Cervantas charges forward in an 40-foot line without provoking opportunity attacks. Any creature in Cervantas's path must make a DC 18 Dexterity saving throw. On a failure the creature is considered hit by the Entangle attack (if Cervantas cannot grapple any more creatures the creature is knocked prone instead).