Mighty Swarm. Once on each of its turns, after hitting a creature with an attack, Zyaradil may have the swarm act in one of the following ways.

• The attack's target takes 1d8 piercing damage from the swarm.
• The attack's target must succeed on a Strength saving throw DC (18) or be moved by the swarm up to 15 feet horizontally in a direction of your choice. It also falls prone.
• Zyaradil is moved by the swarm 5 feet horizontally in any direction. This can trigger Opportunity Attacks. When moved this way, Zyaradil gains half cover until the beginning of its next turn (+2 to AC/Dex saving throws).

From the Depths. Zyaradil gains disadvantage on attack rolls for 1 turn if exposed to bright light.

Call the Swarm. 3/Long Rest. Summon a Swarm of Hordelings with 10d10 hp. It forms into a creature based on its HP following the Form ability chart.

Multiattack. Zyaradil makes two attacks per turn. It may forgo one of its attacks to Call the Swarm.

Swipe. Melee Weapon Attack: +9 to hit, reach 5 ft., 1 target. Hit: 1 (1d10 + 4) piercing damage.

Hurl the Swarm. 60ft cone. Any creature within the cone rolls a Dexterity DC(18). On fail it takes 3d8 damage, and half that amount on a success.

Writhing Tide. 5/Long Rest. Zyaradil calls the swarm to surge up underneath him, and gains fly speed 10ft. It remains hovering until the beginning of its next turn.

 Swarming Resistance. 5/Long Rest. When Zyaradil takes damage, as a reaction it can use it's reaction to give itself resistance to that damage. Zyaradil vanishes into its swarm and then teleports to an unoccupied space that it can see within 30 feet. 

Legendary Resistance. 3/Long Rest. Whenever Zyaradil fails a saving throw, it may instead succeed on that saving throw.