[b]The Kraken[/b]
The Kraken. The First. Alpha. The knowledge around its birth was destroyed together with Atlantis. This ancient, one-eyed monster’s tentacles often cast the last shadow over those unfortunate enough to enter its grounds. For those with a little more foolish fightning spirit, the Kraken has another weapon. Its mouth. With 5 rows of viciously sharp teeth it can shred you to pieces before you even fall into its stomach. Feared and infamous, the Kraken now lays dormant at the Trench. Waiting for the One Song to wake it up.
[b]
Jormungand[/b]
Serpent. End. Slayer of the Alfather. Jormungand is a massive sea-serpent. The Norn thought that its body kept the seas together. Jormungand is far less known that his cousin, the Kraken. Though equally, if not more dangerous. He prefers to play with its prey, winding around a ship and see who will jump and who will fight. His spit is also toxic. The Great Serpent also lays beneath the Trench, waiting for the Song of Ragnarok to wake it up.
[b]
Leviathan[/b]
Guardian. Destroyer. Traitor. Misguided One. Many suspect that Leviathan was the cause of the destruction of Atlantis. The massive lobster is surprisingly agile in the water. It was once the great guardian of Atlantis. No human ship could even near the legendary city without encountering this destructive force given shape. Now, after Atlantis’ Doom, the Leviathan still roams the waters, protecting the Sunken City’s secrets. Unlike his brothers, Leviathan doesn’t need to be woken up. Instead, it needs new orders, given to him through an unknown song. Leviathan is said to be the strongest of the three.

[b]Eldrich[/b]
An old story still told by gibbering old human and mere-people women alike. “Before this city. Before our king. Before Atlantis. Before the three Ancients, there was Eldrich. He gave birth to the three Ancients. And they began to roam the oceans.” Is the only few sentences left about the story. For some odd reason, both humans and mer-people know about Eldrich. Though his existences has never been proven. There were never sightings of him. Only a few self-proclaimed prophets. Though, if Eldrich is real, the creatures of the world have good reason to fear him.

So anyway, I made a quick few 'descriptions' of the Ancients or the monsters Atlantis could control. As always, these are just suggestions.

I make Eldrich simply to keep something more open. Like telling people that there is a distinct possibility that there is more. Just not right now.