Kartir is a Zoroastrian high priest who decided there was only one heaven and one hell. He removed all images from the altars, leaving only the fire (Atar). He was responsible for the condemnation and execution of Mani (274-277 AD), as recorded in the Skronamon Document.
Mani is his antagonist. GRDT and KAXA are followers of the Manichaean duality that Kartir persecuted (see Graz’zt / GRDT).