Cocytus

Legendary Resistance (3/day). If Cocytus fails a saving throw, he can choose to succeed instead.

Cold Aura. Any creature hostile to Cocytus that starts its turn within 100 feet of Cocytus must make a DC 16 Constitution saving throw. On a failed save, the creature takes 2d8 cold damage. On a successful save, the creature takes 1 cold damage. This does not effect downed creatures.

Action Surge (3/day). Cocytus may take an extra action.

Multiattack. Cocytus makes 4 attacks. 2 with his halberd, and 2 with his katana, or 1 of each and his breath weapon.

Katana. Melee Weapon Attack: +18 to hit, reach 5 ft., 1 target. Hit: 27 (5d6 + 10) slashing damage. 

Halberd. Melee Weapon Attack: +18 to hit, reach 10 ft., 1 target. Hit: 32 (4d10 + 10) slashing damage.

Breath Weapon. Cocytus exhales ice in a 30-foot cone. Each creature in that area must make a DC 15 Dexterity saving throw, takeing 33 (6d10) cold damage on a failed save, or half as much damage on a successful save.

Ice Infusion. Add 2d6 cold damage to 1 weapon until the start of Cocytus' next turn.

Cocytus can take 3 Legendary actions, Choosing from the options below. Only one option can be used at a time and only at the end of another creature's turn. Cocytus regains spent legendary actions at the start of his turn.

Katana Swing (Costs 1 Action). Cocytus may take a swing with his katana.
Halberd Swing (Costs 1 Action). Cocytus may take a swing with his halberd.

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Mythic Action Name (Costs # Actions). Enter the description for your mythic action.