Kruthiks were created through vile magics by an ancient tiefling empire on the world of Nerath for use as living siege weapons. The beastmasters infused the essence of a fiendish burrowing insect from the Nine Hells into scytheclaw drakes, creating the first kruthiks. The monstrous creations proved impossible to control and they quickly escaped into Nerath's Underdark during the empire's fall. Unleashed into the world of Nerath, kruthiks thrived and became one of the greatest threats that the subterranean civilizations of the Underdark, as well as their neighbors on the surface, faced.
Kruthiks became more horrid as they advanced through their life cycle, but all kruthiks shared certain characteristics. A kruthik vaguely resembled a canine covered in plates of thick, silvery chitin. It had six limbs composed of bone, chitin, and steely scales; the front and rear appendages ended in long scythes that could hew through stone. In addition to serving as a kruthik's weapons, manipulators, and means of travel, these limbs were its main sensory organs. Its reptilian head was mostly large, serrated mandibles. Armored plates protected a kruthik's neck and back.
— Theros Silveraxe, Dwarf Darkstrider
These sadistic half-reptiles were an unyielding force of chaos and destruction. They turned quickly on their failed masters and, given their burrowing capabilities, easily wandered off and massacred whatever they found.
Kruthiks were aggressively territorial and would defend their hives, especially the nest's hatchery, and food stores.
Kruthiks communicated with each other through complex insect-like chitters, reptilian hisses, and pheromones. They were intelligent enough to understand simple phrases in other languages.
These monstrosities hunted in packs. The hatchlings and the young swarmed around the nearest foe in a vicious horde, raking the target to pieces with their claws and mandibles and fighting until slain. The adults used their toxic spikes on tempting targets within range before engaging in melee. Similarly, the hive lords used acid blasts to weaken enemies then followed with relentless claw attacks, while staying close to other kruthiks.
When a kruthik was in contact with the ground, it could detect the slightest vibrations, allowing it to pinpoint the location of any creature within a 50-foot (15 meters) radius.
Kruthiks reproduced once a year by laying a clutch of six gray eggs that hatched a day or two later. The hatchlings were the size of a small dog but could easily rend a humanoid in half. After a week of constant feeding, a hatchling became a young kruthik, which was almost 3 feet (9 meters) long and weighing 30 pounds (13 kilograms). Young kruthiks had dragonfly-like wings, but most of them couldn't fly, with the wings instead giving them a speed advantage over their older kin. After a year, a kruthik matured into an adult, which was over 6 feet (1.8 meters) long and weighing 250 pounds (113 kilograms)).
Adult kruthiks developed chitinous spikes on their plates that filled with acerbic venom when threatened. Those spikes could also be hurled short distances with deadly accuracy.
Most kruthiks died before reaching their final stage of life at five or more years. That stage was the hive lord; they encased themselves in a dull gray-blue chrysalis and after four weeks of metamorphosis emerged covered with bulkier chitin plates, nearly 12 feet (3.6 meters) long and weighing a ton (907 kilograms). The hive lords had highly caustic and nauseating blue saliva, which they could spray in a wide arc.
Kruthiks were social creatures dwelling in hierarchical nomadic hives, which typically consisted of numerous kruthiks led by one or more hive lords. The hives depleted all resources in the area and moved on. Kruthiks inhabited large underground chambers or cave systems. They were attracted to sources of heat and magical energies, especially those connected to the Nine Hells, and excavated lairs as close to such locations as possible.
Because kruthiks were repelled by the sulfurous smells of their dead, there was a thriving market for their ichor and body parts. Armorers were able to use kruthik chitin to create lightweight yet durable armor and shields.
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Mike Mearls, Jeremy Crawford (May 29, 2018). Mordenkainen's Tome of Foes. Edited by Kim Mohan, Michele Carter. (Wizards of the Coast), pp. 211–212. ISBN 978-0786966240.
- ↑ 2.0 2.1 Mike Mearls, Stephen Schubert, James Wyatt (June 2008). Monster Manual 4th edition. (Wizards of the Coast), pp. 170–171. ISBN 978-0-7869-4852-9.
- ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 3.13 Tim Eagon (December 2013). “Ecology of the Kruthik”. In Steve Winter ed. Dragon #430 (Wizards of the Coast), pp. 39–43.
- ↑ 4.0 4.1 4.2 4.3 Mike Donais, Skaff Elias, Rob Heinsoo, and Jonathan Tweet (October 2003). Miniatures Handbook. (Wizards of the Coast), pp. 63–65. ISBN 0-7869-3281-3.
- ↑ 5.0 5.1 David Noonan and Greg A. Vaughan (September 2008). Scepter Tower of Spellgard. (Wizards of the Coast), p. 14. ISBN 978-0-7869-4954-0.