Meat, mostly

With each other.

They have the ability to change colors to match their surrounding, they have three hearts (making them hard to kill), and they can produce ink, though it tires them greatly.

Generally, gremkaul are conniving, ambitious bastards who will lie, deceive, and murder their way to the top of the local food chain, so to speak. They are known to revere krakens (giant squid demons of the deep).

Gremkaul society is centered in their home nation of Kaulurkaunimian in the depths of the Aurul Ocean (northeast of Monbaru by about 1500 miles and lower by about a mile or ten). Their society is driven by the pursuit of individual gain, and the gremkaul "dream" is to be as puissant as the kraken, the great demonic squids that lurk in the darkest parts of the world's oceans, ruling their own domains as fearsome tyrants.

Like real squid(s?), gremkaul lay eggs. The eggs are left in a communal chamber in the center of their vast temple-cities, then ignored. The young hatch and are left to fend for themselves from the scraps deposited on the outer rims of the chamber by the city--they are left with the trash and left to figure out how to survive. As such, only the smartest and toughest of them survive. When they are strong enough to swim out of the chamber (it being specially pressurized to make this difficult), they are immediately forced to serve their elders. For years, they are treated like slaves (which they are) and forced to work hard. If they are bad at the work they are given, they are usually beaten and shamed, then sent to work on a different task. In this way, they are taught to avoid failure and simultaneously tested to find their strengths.

Usually, if the child survives, they are apprenticed to a master by the age of 8. Their tutelage under their master is grueling and horrific, but those that survive are often very skilled at what they do. In order to be a full citizen of Kaulurikaunimian, they must prove themselves worthy in the eyes of their master--or kill their master. Those that fail either of these are either killed or banished.

The religion of the gremkaul society focuses on the deity people on the surface call the Webweaver and associated with spiders. He is the master manipulator, the most subtle of liars, and the Lord of the Hells, God of Darkness, etc. Underwater, he is associated with the kraken and known as the Tentacled God. They also pay respects to the fallen goddesses that came before him--the Dark Mother of the Depths (ambition incarnate) and the Blood Goddess (brutality incarnate).

Mages are rare, but since gremkaul society has a high mortality rate amongst the weak, those who exhibit magical ability actually seem to crop up more often because it quickly pulls them into an appropriate apprenticeship and a way out of servitude. Magical ability is highly valued.

Kraal is through the same apprentice system the others go through. You simply have to have been skilled enough to attract the eye of one of the powerful. One becomes Autocrat by killing the previous Autocrat. This has lead to a line of extremely powerful Autocrats who have kept alive via every trick in the book--and through use of Gifts. Instability would reign in gremkaul society if it weren't for the sheer difficulty it takes to actually kill an Autocrat.