Guardians

The sea monsters that reside in The Upper Layer are referred to by most as Guardians. Coming in a variety of shapes and sizes ranging from regular sized fish with teeth capable of rending solid steel to miles long eels that wrap their constricting bodies around anything foreign that enters the Upper Layer. Different Guardian species bear resemblance to smaller species throughout the lower depths of the Shattered Sea leading some biologists to view the Guardians as ancient ancestors of the modern day species. 
The diet of a Guardian seems to be composed of anything that enters the Upper Layer. Guardians have not been observed attacking each other yet occasionally a Guardian will be spotted with a large bite mark taken out of it.
Guardians stay in the Upper Layer exclusively except for when they reach the end of their lives. When a Guardian grows old it makes its way down to the Chalk Towers and die. These corpses are harvest for their parts by salvagers and scavengers. Guardian parts fetch a high price and have a wide variety of uses. Their harder parts, teeth, bones, chitin, scale and the like, are used in weapons, armor and building supplies. Their fluids are used in potions, tinctures and other magical effects.