Unikraken

Charge. If the unikraken moves at least 20 feet straight toward a target and then hits it with a horn attack on the same turn, the target takes an extra 9 (2d8) piercing damage. If the target is a creature, it must succeed on a DC 30 Strength saving throw or be knocked prone.

Innate Spellcasting. The unikraken's innate spellcasting ability is Charisma (spell save DC 14). The unikraken can innately cast the following spells, requiring no components:

At will: detect evil and good,druidcraft, pass without trace

1/day each: calm emotions, dispel evil and good, entangle

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

Magic Weapons. The unikraken's weapon attacks are magical.

Amphibious. The unikraken can breathe air and water.

Freedom of Movement. The unikraken kraken ignores difficult terrain, and magical effects can't reduce its speed or cause it to be restrained. It can spend 5 feet of movement to escape from nonmagical restraints or being grappled.

Siege Monster. The unikraken deals double damage to objects and structures.

Horn. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) piercing damage.

Healing Touch (3/Day). The unikraken touches another creature with its horn. The target magically regains 11 (2d8 + 2) hit points. In addition, the touch removes all diseases and neutralizes all poisons afflicting the target.

Teleport (1/Day). The unikraken magically teleports itself and up to three willing creatures it can see within 5 feet of it, along with any equipment they are wearing or carrying, to a location the unikraken is familiar with, up to 15 miles away.

Multiattack. The unikraken makes three tentacle attacks, each of which it can replace with one use of Fling.

Bite. Melee Weapon Attack: +17 to hit, reach 5 ft., one target. Hit: 23 (3d8 + 10) piercing damage. If the target is a Large or smaller creature grappled by the unikraken, that creature is swallowed, and the grapple ends. While swallowed, the creature is blinded and restrained, it has total cover against attacks and other effects outside the unikraken, and it takes 42 (12d6) acid damage at the start of each of the unikraken's turns.

If the unikraken takes 50 damage or more on a single turn from a creature inside it, the unikraken must succeed on a DC 25 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the unikraken. If the unikraken dies, a swallowed creature is no longer restrained by it and can escape from the corpse using 15 feet of movement, exiting prone.

Tentacle. Melee Weapon Attack: +17 to hit, reach 30 ft., one target. Hit: 20 (3d6 + 10) bludgeoning damage, and the target is grappled (escape DC 18). Until this grapple ends, the target is restrained. The unikraken has ten tentacles, each of which can grapple one target.

Fling. One Large or smaller object held or creature grappled by the unikraken is thrown up to 60 feet in a random direction and knocked prone. If a thrown target strikes a solid surface, the target takes 3 (1d6) bludgeoning damage for every 10 feet it was thrown. If the target is thrown at another creature, that creature must succeed on a DC 18 Dexterity saving throw or take the same damage and be knocked prone.

Lightning Storm. The unikraken magically creates three bolts of lightning, each of which can strike a target the unikraken can see within 120 feet of it. A target must make a DC 23 Dexterity saving throw, taking 22 (4d10) lightning damage on a failed save, or half as much damage on a successful one.

Fire Breath (Recharge 5–6). The unikraken exhales fire in a 25-foot cone. Each creature in that area must make a DC 26 Dexterity saving throw, taking 21 (6d6) fire damage on a failed save, or half as much damage on a successful one.

The unikraken 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. The unicorn regains spent legendary actions at the start of its turn.

Shimmering Shield (Costs 2 Actions). The unikraken  creates a shimmering, magical field around itself or another creature it can see within 60 feet of it. The target gains a +2 bonus to AC until the end of the unikraken's next turn.

Heal Self (Costs 3 Actions). The unikraken magically regains 24(3d12+ 2) hit points. 

Ink Cloud (Costs 3 Actions). While underwater, the unikraken expels an ink cloud in a 60-foot radius. The cloud spreads around corners, and that area is heavily obscured to creatures other than the unikraken. Each creature other than the unikraken that ends its turn there must succeed on a DC 23 Constitution saving throw, taking 16 (3d10) poison damage on a failed save, or half as much damage on a successful one. A strong current disperses the cloud, which otherwise disappears at the end of the unikraken's next turn.