The conversion chamber is where The Beginner and Mardock landed once and met a Cyberman who wanted to convert them. The Beginner managed to escape (Convertion), accidently leaving Mardock behind (2012). 

A battle between the Beginner, The Writer, Spike Dimentos, Silence, Daleks and Rock kind against the Death and the Cybermen arose. Having previously landed in order to find Jo's body, it turns out that she was converted partially into a Cyberman, however as her conversion was triggered by the three Beginner's regeneration energy she wasn't completely converted and was able to - along with Mardock - kill the Death, causing the conversion chamber to blow up. (Battle of the Beginner