Ursarax similar to the Thallax in design are the Mechanicum's Assault Marines equivalents. Ursarax are advanced Jump Pack-equipped Tech Thralls of the Adeptus Mechanicus designed in the later Great Crusade. They were first designed by Magos Explorator Enabrin Falkan as a heavy, rapid-moving close combat unit. Using a fusion of existing technologies sacred to the Mechanicum, materials and patterns taken from the Thallax of the Ordo Reductor, and the fruits of Falkan's own discovered, he created a unit of mass rape.
Like the Thallax, they are Thralls rather than Servitors, selected from suitable human candidates for conversion so their living components retain a consciousness and dim recollection of their former selves. Neural anesthesia is automatically administered for the successful fulfillment of their orders, providing them with temporary relief from their tortured existence. After Falkan's mysterious disappearance, his warring acolytes dispersed to many different masters, taking the secret of the Ursarax with them. It is unknown if any Ursarax are still in existence, but chances are that they are probably mothballed in a museum for the Tech Priest to goggle at, knowing the Mechanicum nowadays.
Ursarax are equipped with Lightning Claws and Volkite Incinerators. Great for tearing apart MEQ's and GEQ's alike. Far more useful than Chaos Warp Talons that for sure. They also have a hug of doom (get it? Ursa, like bears) for TEQs.