Beta Titan: Scylla

Amphibious nature. Scylla can breath Water and Air

Freezing Home. Any water in 1 mile radius that Scylla is in cools to sub zero temperatures. Any creature in the water takes 10 cold damage.

Titan power. Scyllas attacks count as magical in order to overcome resistances. 

Legendary Resistance (3/Day). If Scylla fails a saving throw, it can choose to succeed instead.

Multiattack . Scylla makes six leg attacks and 10 tentakel attacks on its turn. 

Leg Attack. Melee Weapon Attack: +15 to hit, reach 50 ft., 1 target. Hit: 35 (4d10 + 15) piercing damage.

Tentacle Attack. Melee Weapon Attack: +15 to hit, reach 20 ft., 1 target. Hit: 15 (1d10 + 10) bludgeoning damage. Any creature hit by the tentacle must succeed a DC 20 strength save or be grappled by the tentacle. Scylla can grapple ten creatures. A grappled creature automatically takes the tentacel damage on the beginning of its turn.

Infectious Bacteria (recharge 5 6). Any creature in the same water as Scylla and within 200 ft. radius takes 75(10d10+20) necrotic damage and be diseased or half as much if they succeed a DC 25 constitution saving throw and no further effects.

Scylla 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. Scylla regains spent legendary actions at the start of its turn.

Infectious Bacteria (3 Actions). Scylla recharges her infectious bacteria action and uses it.

Tentacle (1 action). Scylla makes three tentacel attacks.