Depth of Despair: Anyone who comes in contact with Zhast'olan rolls a Wisdom saving throw with DC 30, or they are given 2nd Level Exhaustion.

Eyes of Zhast'olan: Zhast'olan can see and sense any creature that comes within a 100 mile radius of him

Unstoppable: This creature is immune to Charm, Fear, Petrification and any spell that requires a wisdom or intelligence saving throw.

Aura of the Depth: All water 10 Miles around Zhast'olan turns into a necrotic fluid, colored purple.

Soul Bound: Any creature that is killed by Zhast'olan vanishes into purple dust and is soulbound in Zhast'olan's head.

Head Count: Zhast'olan strikes once for every head he has.

Endless Ocean: Once Zhast'olan picks a target in an ocean, he transports them unknowingly into his realm of an endless ocean.

Devour: Zhast'olan attempts to Devour his target dealing  10d10 Necrotic Damage for every turn they are stuck in his mouth, saving throw is 20 Dexterity.

Eyes of the Depth: Zhast'olan makes eye contact with a target as they are shown their greatest fear, Wisdom Saving throw or be feared for 5 turns. and take 5d10 of Psychic Damage (DC 25)

Beam of Necromancy: One of Zhast'olan's heads shot a laser beam that deals 8d12 Necrotic Damage on impact. (DC Dex 20)

Necrotic Breath: Zhast'olan breaths a 50 feet cone of Necrotic Unextinguishable fire that floats on water, dealing 5d10 of damage to anyone who touches it. (increasing damage by 1d10 for each turn it is kept) (DC Dex 20)

Eyes of Wisdom: Zhast'olan makes eye contact with a target, charming them to follow his orders for 5 turns, if charmed the target cannot take damage, all damage dealt to the target is halved and dealt to Zhast'olan instead. (DC 25)

Tail Swipe: +15 Zhast'olan swipes his tail attacking anyone in its way, dealing 6d12 bludgeoning damage, and poisoning them with 1d12 each turn for 5 turns (can stack)

Counterspell:
Zhast'olan rolls a d20
1-5: Level 1 -> Level 3 Spells
6-8: Level 1 -> Level 4 Spells
9-10: Level 1 -> Level 5 Spells
11-13: Level 1 -> Level 6 Spells
14-17: Level 1 -> Level 7 Spells
18-19: Level 1 -> Level 8 Spells
20: Level 1 -> Level 9 Spells

Ocean of Necromancy: The ship if not resistant to Necromancy, starts to disintegrate into the ocean, anyone who touches the water takes 5d10 of Necromancy Damage each turn.

Ray of Unending Necromancy: Zhast'olan may use this ability once every year, if he uses this ability he loses half of his hitpoints or dies if below 500 hp. Once he uses it, if he does not die, he enters a state of hibernation for 6 months. All of Zhast'olan's heads charge an attack for 2 turns before launching it on the third. He shoots a 120 feet wide and 5000 feet long ray of Necrotic Energy, disintegrating anything it hits in the way dealing 10d100 Necrotic Damage. Any creature hit by this attack has the curse of the depths applied to them, making them unrevivable after death unless the curse is somehow broken. (29 Dexterity Saving Throw)