Blood Moon Leviathan

Lunar Tides.

The presence of the Blood Moon Leviathan warps the ocean and sky:

• At the start of its turn, the Leviathan pulls all creatures and structures within 120 feet 10 feet closer to it. Any creature moved in this way must make a DC 22 Strength saving throw or be knocked prone.
• The Leviathan can magically control the tides, causing massive waves. As a bonus action, it can flood a 100-foot radius, turning the area into difficult terrain and submerging non-flying creatures. Creatures that cannot swim must make a DC 20 Strength saving throw or begin drowning.

Hunger Eternal.

The Leviathan’s insatiable hunger can never be quenched. It can swallow entire buildings, and any creature reduced to 0 hit points by it is permanently devoured, unable to be resurrected except by a Wish spell.

• When the Leviathan reduces a creature or structure to 0 HP, it regains hit points equal to half the damage dealt.
• When the Leviathan starts its turn, all creatures within 30 feet of its mouth must make a DC 22 Dexterity saving throw or be pulled into its maw.

Multiattack.

The Leviathan makes three attacks: one with its Bite, one with its Tail, and one with Crimson Maw if available.

Bite. Melee Weapon Attack: +17 to hit, reach 20 ft., one target.

Hit: 60 (8d12 + 10) piercing damage plus 18 (4d8) necrotic damage. If the target is a Huge or smaller creature, it must make a DC 22 Dexterity saving throw or be swallowed. A swallowed creature is blinded and restrained, has total cover from outside effects, and takes 42 (12d6) acid damage at the start of each of the Leviathan’s turns. If the Leviathan takes 50 or more damage in a single turn, it must make a DC 20 Constitution saving throw or regurgitate all swallowed creatures, which fall prone within 10 feet of it.

Tail Slam. Melee Weapon Attack: +17 to hit, reach 30 ft., one target.

Hit: 48 (6d10 + 10) bludgeoning damage, and the target must make a DC 22 Strength saving throw or be knocked 30 feet away and prone.

Crimson Maw (Recharge 5–6).

The Leviathan lets out an unearthly roar, invoking the Blood Moon’s power. Each creature within 90 feet must make a DC 22 Wisdom saving throw or be frightened for 1 minute. While frightened in this way, a creature’s maximum HP is reduced by half until the effect ends. A frightened creature can repeat the save at the end of its turns.

The Blood Moon Leviathan can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time, and only at the end of another creature’s turn. It regains spent legendary actions at the start of its turn.

• Tidal Surge. The Leviathan moves up to half its speed, ignoring difficult terrain. It does not provoke opportunity attacks.
• Lashing Tail. The Leviathan makes one Tail Slam attack.
• Eclipse Devourer (Costs 2 Actions). The Leviathan inhales, pulling all creatures within 60 feet 20 feet closer. Creatures that fail a DC 22 Strength saving throw are pulled into its mouth and must succeed on a DC 22 Dexterity save or be swallowed.