The Cell-Kin are a little-known intelligent alien race who attacked a company of the Subjugators Space Marine Chapter during a protracted campaign in the Technetium Belt, which occurred sometime in the 41st Millennium. The unique reproductive cycle of the species made their complete eradication very difficult to achieve.
Several Astartes of the Subjugators' 3rd Company were infected by the insidious xenos, who breed by viral dissemination. Their DNA infects the body of the host, where it will literally reshape the host in its own image, that of a flabby and semi-amorphous humanoid, with eyes spread randomly around its head, this being the Cell-Kin's true form.
Though the Space Marines' enhanced genetic make-up and immune systems proved largely resilient to this threat, 20 Battle-Brothers of the 3rd Company were lost in the early stages of the campaign as they were slowly mutated into new, hideous forms. The Chapter's Apothecaries identified the threat, but too late to save those Battle-Brothers already affected by the Cell-Kins' infection. The infected Brethren that survived the conflict escaped and are assumed to be at large in the galaxy to this day. There is little other information on this obscure xenos species.
- Index Astartes IV, "Rogue Sons - Renegade Space Marine Chapters"