Akhelian Leviadon

Void Drum. While other friendly creatures are within 30 ft of Akhelian Leviadon, ranged attacks made towards them are made with disadvantage. 

Magical weapons. Akhelian Leviadon's weapons attacks are magical.

Legendary Resistance (3/day). If Akhelian Leviadon fails a saving throw, it can choose to succeed instead

Echolocation. Akhelian Leviadon can't use its blindsight while deafened.

Amphibious: Akhelian Leviadon can breathe both air and water. 

Multiattack: Akhelian Leviadon makes four attacks. One with it's Scythed Fins, one with it's Crushing Jaw and two with it's Razorsheel Harpoon Launchers

Scythed Fins. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 28 (6d6 + 7) slashing damage.

Crushing Jaw. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 43 (6d8 + 7) piercing damage.

Razorshell Harpoon Launchers. Ranged Weapon Attack: +12 to hit, range 80/160ft., one target. Hit: 17 (3d6 + 3) piercing damage. Each creature hit with this attack must make a DC 18 Strength Saving Throw or be pulled 15 ft closer to Akhelian Leviadon.

Crushing Charge (Recharge 5-6). Move up to it's full movement speed in a straight line, even through creatures with the size of Large or smaller. Any creature Akhelian Leviadon moved through must make a DC 18 Dexterity Saving Throw. On a failure, that creatures takes 8d8 bludgeoning damage and is knocked prone. On a success, that creature takes half the damage and is not knocked prone. Akhelian Leviadon must end its movement in an unoccupied space.

Retract. As a reaction to an attack made against Akhelian Leviadon, add 4 AC to Akhelian Leviadon for that attack. This can be done after declaring the number for the attack roll.

Akhelian Leviadon 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. Akhelian Leviadon regains spent legendary actions at the start of his turn.

Traverse the Ethersea (Costs 1 Actions). Teleport to an unoccupied space within 60ft.

Snaping Jaw (Costs 1 Actions). Make an attack with the Crushing Jaw.

Rythmic Distruption (Costs 2 Actions). Enemy creatures holding a concentration spell within 30ft must make a DC 16 Constitution saving throw. On a failure that creature loses concentration and takes 2d6 psychic damage. 

Spinning Maelstrom (Costs 3 Actions). Each enemy creature with 60ft of Akhelian Leviadon must make a DC 18 Strength Saving Throw. On a failure, the creature is pulled up to 20ft closer to Akhelian Leviadon, and if the creature ends this movement within 5 ft of Akhelian Leviadon, that creature takes 4d6 bludgeoning damage.