Malkariss was the ultimate ruler of an underground kingdom named after himself. A ruthless tyrant, he enjoyed the suffering of others, and only cared for his own good. He was old and deformed, but lived in a huge limestone statue carved in his likeness, issuing orders to his second-in-command, Nadaz, the leader of a cult-like army of robed rats. Malkariss used slaves to build his kingdom; child slaves kidnapped from their homes. In order to keep his supply of slaves at high numbers (as many of them died from abuse), he hired slavers to continually capture more for him, promising them power and/or land in his kingdom. The most famous of these slavers was Slagar the Cruel, who accepted the job in order to enact his own personal vendettas.
When Matthias the warrior mouse and his allies attacked Malkariss's kingdom after following Slagar there, the polecat lowered himself down from his statue so that he could escape the ensuing battle. He was, however, seen by Matthias, and attemped to use the warrior's own sword to slay him, but a group of his former slaves attacked him and stoned him to death. His underground kingdom soon collapsed upon itself after the battle, and was obliterated.