Replicae are artificial beings created by genetic engineering, the branch of the science known to archaic humans as "cloning." The science was widespread during the Dark Age of Technology, but barely understood in later eras.
Space Marine Replication
Replication has been tried at least twice in the Imperium's history by a Space Marine unit seeking to quickly replace catastrophic losses. Instead of using human recruits, geneseed is used to "grow" clones of previous battle brothers, which can be amalgamations or singular individuals. Ideally, this process should produce a fully mature Astartes, with all of his implanted organs fully developed, and ready for combat in a matter of weeks or months, instead of the years it normally takes to mature and train a Neophyte into a full-fledged battle-brother.
Being one of the many technologies developed in the Dark Age of Technology, a great deal of the processes and techniques for creating successful and functioning clones was lost. These include the purification of the blood to be used in the cloning procedure and the elimination of gene-flaws.
Due to the loss of these techniques, mutations and other deformities occurred in almost every later attempt to repeat the process. These might include extra limbs, claws and fangs and also mental and psychological changes, including fury and predatory bloodlust.
The replicae process can also magnify and accentuate already present gene-flaws. In many cases deformities present in the gene-stock can take disturbing and horrific shapes in the replicae.
- In M31, due to the heavy losses the Raven Guard Legion sustained during the Isstvan V massacre, Corax attempted to replace his numbers and return to combat readiness as quickly as possible. Due to the secretive nature of the Raven Guard chapter, little is known of the success of the chapter's attempt at cloning, however many rumours circulate in the ranks of other chapters describing the outbreak of mutants.
- In M41, in the wake of the disastrous Arkio Insurrection, Apothecary Majoris Caecus of the Blood Angels proposed using replication. Commander Dante disapproved, but Caecus continued his research in secret. Caecus believed he had succeeded with the aid of a mysterious Magos Biologis, but his creations, the Bloodfiends, though at first promising, turned into bloodthirsty monsters, manifesting extreme versions of the Blood Angels' geneseed flaws, the Black Rage and the Red Thirst. It is uncertain how much of this catastrophe was accident caused by Caecus's incomplete knowledge, and how much was deliberately engineered by the Magos (who turned out to be the traitor Fabius Bile in disguise).
- 1: Red Fury (Novel) by James Swallow, [Needs Citation]
- 2: Index Astartes IV, [Needs Citation]
- 3: Deliverance Lost (Novel) by Gav Thorpe, [Needs Citation]