Slardar

[Lamprey]

Slardar is a creature of the Deep Ones, guardian of the great wealth of sunken cities and the ancient wealth buried there. In the lightless gulf of the great ocean abysses, he carries his lure-light with him through the secret treasure rooms, and submarine thieves (sent into the deeps by covetous dryland sorcerers) are drawn in by its friendly glow, never to return. He is utterly loyal, and his taciturn nature hides deep knowledge of the most secret places of the sea. He rises to the shallows in spite of the pain caused him by brightness, to commit reconnaissance, and make sure no one is conspiring against the depths. Because he has spent his whole life at great pressure, under tremendous weight of the sea, he is a creature of great power.

[Chairraider]

Similarly to Tidehunter I wonder WHY he suddenly leaves the depths. Especially considering it pains him? Why would he bother about people possibly "conspiring against the depths" if his job is to basically be a guard? Again it would kinda make sense if somebody stole one of those treasures and Slardar needs to get it back.

[Dinozavre]

I really like what Chair said in the Tidehunter thread, and it would make a lot of sense if Slardar was the guardian of Tidebringer and Kunkka somehow stole it and now Slardar has to return it.

[Cymen]

Similarly to Tidehunter I wonder WHY he suddenly leaves the depths. Especially considering it pains him? Why would he bother about people possibly "conspiring against the depths" if his job is to basically be a guard? Again it would kinda make sense if somebody stole one of those treasures and Slardar needs to get it back.

What I gather from the description is that the case of "submarine thieves who were sent by dryland sorcerers" is a recent one and the greatest threat to the secrets of the deep. It says he wants to "commit reconnaissance" to find out who sent them. But it does not explain why he joined the battle unless he recognised the source of the thieves. I could be made a little more clear, I guess.
But all in all I like the Slardar-story.

[Znu55]

Or Slardar can be the first one who came to the depth to return the sword, and seeing that he doesn't return tidebringer came too, after a time he summoned morphling , the spirit of the sea, akin to the ebb and flow , he was the a remnant of the great fusion, the fusion of a great sea god( insert any name here) with the Tidebringer, but the sword couldn't handle the entire power, so tidehunter made morphling with the rest of power.

[Lycan]

he is a creature of great power. and speed

you'd have a perfect fit for sprint in here as well.