Blackmask

Hydraulic Leap. The Blackmask may use 20 ft. of movement to jump 40 ft. in any direction to an unoccupied space. It may only do so once per turn. All creatures within 5 ft. of where the Blackmask lands must make a DC 15 Strength saving throw or take 9 (2d8) Bludgeoning damage.

Slippery Form. The Blackmask has advantage on all rolls to resist being Grappled or Restrained. If the Blackmask still has either of these conditions for more than 2 turns in a row by the time it ends its turn, it automatically frees itself at the start of its next turn.

Watery Gates. As long as the Blackmask is touching some sort of water-based fluid (excluding blood), it can expend all of its remaining movement to instantly teleport to a space that touches another water-based fluid, so long as the space is unoccupied. Doing so does not provoke opportunity attacks.

Multiattack. The Blackmask can use Slam or Powerwash up to 6 times total, in any combination. Alternatively, it can replace two attacks from the Multiattack with Whelming Wave.

Slam. Melee Weapon Attack: +11 to hit, reach 10 ft., 1 target. Hit: 15 (2d8 + 6) Bludgeoning damage.

Powerwash. Ranged Weapon Attack: +11 to hit, range 30/60 ft., 1 target. Hit: 13 (2d6 + 6) Piercing damage.

Whelming Wave (Recharge 6). Strength saving throw: DC 20, each enemy in a 50-foot cone originating from the Blackmask. Failure: 30 (8d6) Bludeoning damage and is knocked Prone. Success: Half damage and is not knocked Prone. If the Blackmask has hit a marked creature with an attack at least once since its last turn, the recharge becomes (5-6) instead.

Mark. The Blackmask chooses one creature it can see within 200 ft. and marks it. Only one creature may be marked at a time. A marked creature has disadvantage on saving throws made against the Blackmask, the Blackmask has advantage on attack rolls made against the marked creature, and the Blackmask deals an additional 7 (2d6) Force damage each time it hits the marked creature with an attack.

The Blackmask always knows where the marked creature is, even across other planes. The effect lasts until either the creature or the Blackmask dies, until the Blackmask marks another creature, or until the Blackmask takes at least 30 Thunder damage in one round. If the effect ends by taking Thunder damage, the Blackmask is unable to use this ability again until the end of its next turn.

Marked Transference. Upon taking damage, the Blackmask may transfer half of the damage to a currently marked creature. The marked creature does not benefit from resistance or immunity if damage is taken in this way.

Legendary Action Uses: 3. Immediately after another creature’s turn, the Blackmask can expend a use to take one of the following actions. The Blackmask regains all expended uses at the start of each of its turns.

Double Slam. The Blackmask uses Slam twice.

Hydraulic Jump. The Blackmask uses its Hydraulic Jump.

Aquatic Burial (Costs 2 Actions). A marked creature within 10 ft. of the Blackmask must make a DC 20 Strength saving throw. On a fail, the creature is submerged. A submerged creature is considered Restrained, is deprived of air, and has full cover. The Blackmask may only have one creature submerged at a time. Submerging a creature does not remove its mark. The creature moves along with the Blackmask, including Hydraulic Leap and Watery Gates. At the beginning of each of the Blackmask's turns, the submerged creature takes 14 (4d6) Bludgeoning damage, in addition to the 7 (2d6) Force damage from its mark. Additionally, if the Blackmask takes Lightning damage, the submerged creature automatically takes that damage as well.

At the end of each of the creature's turns, it may attempt to escape by succeeding a DC 18 Strength saving throw. Alternatively, if the Blackmask takes at least 40 points of Thunder damage in one round, the submerged creature is instantly released. If the creature remains submerged and without air for more that 5 sequential turns, it is instantly knocked Unconscious. A submerged and unconcious creature will automatically fail every death saving throw. Only creatures that require air can be knocked Unconscious and die in this way. Even if the creature does not require air, it may still be knocked Unconscious by damage it sustains, and it may still fail its death saves even though they are not automatic fails.