Kruthiks are chitin-covered reptiles that hunt in packs and nest in sprawling subterranean warrens. They are attracted to sources of heat, such as dwarven forges and pools of molten lava, and carve out lairs as close to such locations as possible. As they burrow through the earth, they leave behind tunnels — evidence that is often the first clue to the nearby presence of a kruthik hive. Kruthiks also make use of preexisting underground chambers, incorporating them into their lairs when they can.

Kruthiks communicate with one another through a series of hisses and chittering noises. These sounds can often be heard in advance of a kruthik attack. Whenever their lair is invaded, kruthik guards send out an alarm by rapidly tapping the stone floor with their sharp legs.

Imprinting. Sometimes Kruthiks' eggs are found by humanoids that decide to keep them rather than destroy them. A Kruthik imprints with the first creature it sees once it hatches, meaning that they will regard the creature as their Hive Lord, for the rest of their lives. A Kruthik would die to save the Hive Lord, but it is not a dumb creature; if treated poorly or not fed, a Kruthik will try to stand its ground and become the new Hive Lord, fighting to the death.

Sharp Senses. In addition to having an acute sense of smell, kruthiks can see in the dark and can detect vibrations in the earth around them. They take the scent of their own dead as a warning and avoid areas where many other kruthiks have died. Slaying a sufficient number of kruthiks in one area might cause the remaining hive members to move elsewhere.

Sharper Weapons. Although they can feed on carrion, kruthiks prefer live prey. They kill enemies by impaling them on their spiked limbs, then grind up the flesh and bones with mandibles strong enough to chew rock. When several kruthiks gang up on a single foe, they become frenzied and even more lethal.

Shared Lair. Kruthiks abide the presence of constructs, elementals, oozes, and undead, and use such creatures to help guard their hive. Kruthiks are smart enough to barricade some tunnels and dig new ones that keep their neighbors away from their eggs.

Young War Kruthik 

Kruthiks hatch from eggs laid by female adults. Each egg is about the size of an adult human’s head and hatches within a month. Tiny kruthik hatchlings are harmless, rarely stray far from the nest, and feed primarily on offal and one another. Within a month, the survivors become young kruthiks large enough to hunt and defend themselves. Those trained by Humanoid masters can become menacing war beasts; their natural resilience makes them a monstrous companion capable of handling lesser foes on its own. It has to be remembered that they are not the smartest creature, and will follow just simple orders.