Beachcomber, Legendary Crab

Amphibious. Beachcomber can breathe air and water.

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

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

World Boss. Beachcomber has the maximum hit points for its Hit Dice (224 hp).

Multiattack. Beachcomber makes two Claw attacks.

Claw. Melee Attack Roll: +9, reach 10 ft. Hit: 17 (3d6 + 7) Bludgeoning damage. If the target is a Large or smaller creature, it has the Grappled condition (escape DC 16) from one of two claws. While Grappled, the target has the Restrained condition.

Shell Shield. Trigger: Beachcomber is hit by an attack roll. Response: Beachcomber adds 5 to its AC against that attack, possibly causing it to miss.

Legendary Action Uses: 3. Immediately after another creature’s turn, Beachcomber can expend a use to take one of the following actions. Beachcomber regains all expended uses at the start of each of its turns.

Claw. Beachcomber makes a Claw attack.

Overrun. Beachcomber moves up to its Speed without provoking Opportunity Attacks and can move through the spaces of Large or smaller creatures. Each time Beachcomber enters a creature’s space for the first time during this move, that target is subjected to the following effect. Dexterity Saving Throw: DC 16. Failure: 29 (4d10+7) Bludgeoning damage, and the target has the Prone condition. Beachcomber can’t take this action again until the start of its next turn.