Akkorokamui

Amphibious. Can breathe air and water.

Legendary Resistance (3/Day). Choose to succeed failed save.

Magic Resistance. Advantage: spell/magic effect saves.

Magic Weapons. Weapon attacks are magical.

Offering of Flesh. Can spend 1 min carefully detaching part or all of one of its 100-foot-long tentacles dealing no damage to itself. Tentacle contains a magic-imbued fleshy hook and enough meat for 25 rations (if part of a tentacle) or 50 rations (if a full tentacle) if properly preserved. Fleshy hook remains imbued with magic for 4 hrs or until a creature eats it. A creature that eats magic-infused fleshy hook regains 50 hp then it is cured of blindness deafness and all diseases or restores all lost limbs (creature's choice). Limb restoration effect works like regenerate spell. Hook's magic works only if the akkorokamui offered it willingly.

Regeneration. Regains 15 hp at start of its turn if it has at least 1 hp.

Siege Monster. Double damage to objects/structures.

Multiattack. Three Tentacles. Can replace one with Spellcasting or Healing Touch.

Guardian's Grasp. When a creature akkorokamui can see within 30' is attack target akkorokamui can pull creature out of harm's way. If creature is willing it is pulled up to 10 ft. closer to akkorokamui and akkorokamui becomes new attack target. If creature isn't willing this reaction fails.

Discern. Makes a Wis (Perception) or Wis (Insight) check.

Jet. Swims up to half its swimming speed with o provoking opportunity attacks.

Cast a Spell (2). Uses Spellcasting.

Tentacle Sweep (2). Spins in place with its tentacles extended. Each creature within 20' of it that isn't grappled by it: DC 17 Dex save or take 19 (4d6+5) bludgeoning damage and be knocked prone. Each creature grappled by akkorokamui must make DC 17 Str save or take 12 (2d6+5) bludgeoning damage.