Hold Breath. While out of water, the archeteuthis can hold its breath for 1 hour.

Water Breathing. The archeteuthis can breathe only underwater.

Block. For every tentacle that was not used to attack, the archeteuthis gains +1 AC.

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

Regeneration. The archeteuthis regains 10 hit points at the start of its turn. If the archeteuthis takes acid damage, it regains only 5 hit points at the start of its next turn. The archeteuthis dies only if it is hit by an attack that deals 10 or more acid damage while the archeteuthis has 0 hit points.

Multiattack. The archeteuthis makes up to 8 tentacle attacks.

Tentacle. Melee Weapon Attack: +7 to hit, reach 15 ft., single target. Hit: 8 (1d4 + 6) bludgeoning damage, and the target is grappled (escape DC 18). Until this grapple ends, the target is restrained. The archeteuthis has eight tentacles, each of which can grapple one target.

Bite. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 18 (3d8 + 5) piercing damage. If the target is a Large or smaller creature grappled by the squid, 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 squid, and it takes 14 (4d6) acid damage at the start of each of the squid's turns.

Fling. One Large or smaller object held or creature grappled by the archeteuthis 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.

Ink Cloud (Recharge 6). A 20- foot-radius cloud of ink extends all around the archeteuthis if it is underwater. The area is heavily obscured for 1 minute, although a significant current can disperse the ink. After releasing the ink, the archeteuthis can use the Dash action as a bonus action.