Medusa of the Deep

Amphibious. The medusa can breathe air and water.

Shapechanger. The medusa can use its action to aquire the lower body of a fish, or back into its true form. Equipment worn or carried on its lower body merges into the fish tail. Equipment that merges has no effect until the medusa return to its true form. With the lower body of a fish, the medusa gains a swim speed of 40 ft. and can be mistaken at a distance for a merfolk. Its statistics are otherwise the same in each form.

Innate Spellcasting. The medusa’s innate spellcasting ability is Intelligence (spell save DC 14). The medusa can innately cast the following spells, requiring no material components:

Cantrips (at will): minor illusion, ray of frost

3/day each: blur, cause fear, ray of sickness

1/day: conjure animals (two giant octopi)

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

Surprise Attack. During the first round of combat, the medusa has advantage on attack rolls against any creature that is surprised, and it deals an extra 10 (3d6) damage each time it hits such a creature with an attack.

Multiattack. The medusa makes two poisonous touch attacks, or one tentacle hair attack and one poisonous touch attack. It can also use Paralyzing Gaze before or after making these attacks.

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

Tentacle Hair. Melee Weapon Attack: +7 to hit, reach 5 ft., one creature. Hit: 4 (1d4 + 2) bludgeoning damage plus 14 (4d6) poison damage.

Paralyzing Gaze. The medusa fixes its gaze on one creature within 60 feet of it that it can see and that can see its eyes. The target must make a DC 14 Constitution saving throw. If the saving throw fails by 5 or more, the creature is instantly paralyzed. Otherwise, a creature that fails the save is restrained. The restrained creature must repeat the saving throw at the end of its next turn, becoming paralyzed on a failure or ending the effect on a success. The paralyzation lasts until the creature is freed by a lesser restoration spell or similar magic. A creature paralyzed by the medusa's paralyzing gaze starts suffocating unless magic allows it to breathe underwater.

Ink Cloud (Recharges after a Short or Long Rest). A 20- foot-radius cloud of ink extends all around the medusa 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 medusa can use the Dash action as a bonus action.