Kruthiks burrow through the earth, riddling the Underdark with tunnels. They hunt in packs and nest sprawling subterranean warrens. Kruthiks dig tunnels that remain intact behind them. Often the first clue to the presence of a kruthik hive is a preponderance of such tunnels in the vicinity. Kruthiks communicate with one another through a series of hisses and chitters. A typical kruthik hive is ruled by the largest kruthik, called the hive lord.

Kruthiks are chitinous reptilian hunters that form small hives underground. They use their superior number to overwhelm and devour all other nearby creatures. Kruthiks hunt methodically, stripping one are of prey before expanding their territory. They butcher their kills and carry treasure back to their nesting warrens. Mauled carcasses and strange tracks that look as if they were made by spikes are sure signs of a kruthik horde.