He went under surgery so the doctors could remove a sick organ from his body; however, the anaesthetic failed, and Kristopher remained paralysed but conscious. At that moment, the Celestis opened an aperture in the space-time continuum to give him the Mark of Indenture in exchange for his survival of the operation. Kristopher took the deal and survived the surgery.
After his death, his identity was taken to Mictlan to serve in the Great Hall, which he compared to the White House and the House of Commons. He was there when the Doctor visited and negotiated for the Celestis' non-interference in the Cataclysm. As one of his stipulations, the Doctor made the Celestis promise to release some of their slaves, and with that, Kristopher was released into whiteness. (PROSE: Alien Bodies)