Ziphius

If the ziphius moves at least 20 feet straight toward a target and then hits it with a dorsal fin attack on the same turn, the target takes an extra 27 (5d10) slashing damage.

The ziphius deals double damage to objects and structures.

As a bonus action at the start of its turn, the ziphius can choose one creature within 120 feet that it can see. The ziphius' eyes glow, and the target must succeed on a DC 15 Wisdom saving throw or the ziphius creates a temporary mental bond with the target until the start of the ziphius' next turn. While bonded, the ziphius reads the creature's surface thoughts, choosing to either gain advantage on attacks against that target or cause the target to have disadvantage on attacks against the ziphius.

The ziphius can breathe only underwater.

The ziphius makes one beak attack and one claw attack.

Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 14 (3d6 + 4) slashing damage.

Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) piercing damage.

If the target is a Large or smaller creature, it must succeed on a DC 15 Strength saving throw or be swallowed by the ziphius. A swallowed creature is blinded and restrained, it has total cover against attacks and other effects outside the ziphius, and it takes 14 (4d6) acid damage at the start of each of the ziphius' turns. The ziphius can have only one target swallowed at a time.

If the ziphius takes 20 damage or more on a single turn from a creature inside it, the ziphius must succeed on a DC 13 Constitution saving throw at the end of that turn or regurgitate the swallowed creature, which falls prone in a space within 10 feet of the ziphius. If the ziphius dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 20 feet of movement, exiting prone.

Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 20 (3d10 + 4) slashing damage.