The Daemonculaba was a hellish fusion of Daemonic power and biological science that that permitted the Iron Warriors to create new Chaos Space Marines. It was constructed within the fortress of Khalan-Ghol, home of the Warsmith Honsou, following his victory at Hydra Cordatus where he had stolen a considerable amount of gene-seed.
The system began with the fattening of human female slaves, who were shackled in cages and force-fed nutrients, widening their bodies to grotesque proportions; these women became part of the Daemonculaba's birthing wombs. Their insides were altered and chemistry wired by the Savage Morticians (possibly members of the Dark Mechanicus), utilising the captured gene-seed. The exact science is vague, but by taking an adolescent child and sealing him within the stomach of one of the enslaved women, the process would either transform the child into an Astartes, or mutate horribly and create an abomination. Either way, the candidate is reborn later without flesh. If the freshly born creature passes inspection, the new recruit is clothed in flesh carved from human male slaves, whose skin had been stretched considerably to vast expanses. If it fails, the reject is cast out through the fortress' sewer system. Some of these rejects survive, however, and become scavenger-hunter creatures known as the Unfleshed.
The system can also utilise the genetic material of harvested Iron Warrior corpses, which are broken down to be fed to the implanted child within the Daemonculabula.
Uriel Ventris of the Ultramarines was briefly trapped inside one of the Daemonculabula, which extracted some portion of his gene-seed and his memories and implanted them onto a clone who became known as The Newborn.