K'tcar'ch was one of the mercenaries stationed on Ry'leh to guard a creature posing as Azathoth.
Though generally resistant to mind control, some of the Shlangii were converted by her into acolytes, including K'tcar'ch. He helped Sherringford Holmes manipulate Baron Maupertuis to attack Ry'leh. The distraction allowed Azathoth to be freed from her prison in Kadath in the Cold Wastes, so she could be brought to the Plain of Leng and escape through a dimensional gateway to Earth. First meeting the Seventh Doctor in London, K'tcar'ch had completely transformed into a Rakshassa when the Doctor encountered him again on Ry'leh. (PROSE: All-Consuming Fire, AUDIO: All-Consuming Fire)