Monstrous Monday: Leviathan

Have not done one of these in a long time.

I thought it would be nice to present a monster from my new Warlock for Swords & Wizardry book.

In the book I introduce some new demonic races including the Eodemons or the Proto-demons.  These are creatures that lived in the lower planes long before the devils were cast down or the demons were there.  Warlocks can beseech the Eodemons for power, but there is always a danger.

Here is the Eodemon Leviathan.
Leviathan has featured in a number of my games and is the destroyer of worlds. "He" eats magic and is attracted to worlds full of magic. "He" has destroyed a number of worlds already in my multi-verse and he hungers for more.
Warlock can choose the Leviathan as a Patron, but doing so makes the Leviathan aware of the warlock's own world.  Some warlocks believe that tapping into the Leviathan's power weakens him and keeps him in a sedated state.

Leviathan
Hit Dice: 25 + 19 (131 hp)
Armor Class: -6 [25]
Attacks: 1 bite (4d6)
Saving Throw: 3
Special: Capsize, digestive acid, swallow whole, dominate and summon water-borne creatures, spells, +2 or better weapon to hit, immunity to fire, electricity, and poison, magic resistance (100%), telepathy 100 ft.
Move: 24 (swim) / 9 (ground)
Alignment: Chaos
Challenge Level/XP: 34/8,600
This monster is believed to be is the oldest of all the Eodemons.  Leviathan is so ancient that even other demons seem in awe of “his” age and power.  It is assumed that it is a "he" though there is no evidence to suggest either way. Leviathan exists only for one purpose; to feed.  Leviathan can be found in the Astral realms devouring entire worlds.
"He" spends his time in the deepest parts of the oceans of the worlds that Leviathan visits. Here he consumes all living forms and is drawn to the world with strong magic.  After devouring 800,000 levels/hd of magical life Leviathan will then be strong enough to destroy the entire world.  From there he moves to a new world where he rests before starting the cycle anew.
Leviathan is completely immune to all magical attacks. Consequently, he is incapable of using magical attacks or spells.

Leviathan can appear as a large sea monster, whale or other great gargantuan creature.

Powerful Warlocks that share Leviathan's desire for the destruction of magic and the world can become his Exarchs.  The Hand of Leviathan and the Voice of Leviathan are his heralds.  The Hand appears first to destroy and sacrifice powerful spell casters. The Voice proclaims the return of their lord and opens the gate to allow Leviathan to swallow a world whole.
Killing these heralds does not stop the coming of Leviathan, but it does slow him down.