Altellax's Swarm of Spawn Tentacle

Swarm. When the Swarm of Spawn Tentacle lost 1/4 hit points, it permanently reduces the maximum hit points of this creature by that lost amount. The amount of creature(s) that can be Grappled by Tentacle Lash is reduce by 1. When the Swarm of Spawn Tentacle is down to their last 1/4 of their hit points, this creature's stats and size becomes Altellax's Spawn Tentacle's stat block.

Void Absorption. Whenever Swarm Spawn Tentacle takes Void Damage,  it is healed instead.

Multiattack. Make one Tentacle Whiplash or three Tentacle Lash

Tentacle Lash. Melee Weapon Attack: +12 to hit, reach 15 ft., one target. Hit: 20 (2d12 + 7) Bludgeoning damage. After dealing damage, the creature makes a DC 20 Dexterity Saving throw, on fail the creature is then Grappled and moved into being 5 ft. of Swarm of Spawn Tentacle. Can Grapple up to four creature(s) at once. Cannot not use this attack if Grappling a creature.

Tentacle Whiplash (Recharge 5-6). Can only use this Action if the Swarm of Spawn Tentacles has equal to or higher than half of it's original hit points. Sphere 15 ft. with the Swarm of Spawn Tentacles as the center. All creature(s) must makes a DC 20 Dexterity Saving throw, on success half the damage and no additional effects. Take 37 (4d12 + 7) Bludgeoning damage, the creature is then Grappled and moved into being 5 ft. of Swarm of Spawn Tentacle. 

Crushing Grip. If Swarm of Spawn Tentacle has a creature(s) Grappled. The creature makes a DC 20 Constitution Saving throw on success half the damage. Deal 20 (2d12 + 7) Bludgeoning damage.