Aamin Marritza served in the Cardassian Guard as a filing clerk and later as an instructor in the same discipline. His posting to the Gallitep labor camp on occupied Bajor would be a source of endless torment in his life. (DS9: "Duet")
While serving at Gallitep, the sufferings of the Bajoran prisoners so grieved him that it sometimes drove him to hide under his desk, covering his ears and weeping as the prisoners cried out for mercy.
After the camp's liberation in 2357, his witnessing of such atrocities continued to haunt him both in the physical legacy of Kalla-Nohra syndrome (a disorder peculiar to those present for a serious mining accident at Gallitep) as well as spiritually. He loathed himself, believing himself a coward for having taken no action to better the Bajorans' situation and continuing to serve as a part of Gul Darhe'el's staff in full knowledge of what he was, in some way, allowing Darhe'el to continue to do.
After the Cardassian withdrawal from Bajor, Marritza took up a posting at a military academy on Kora II--and while still in this position, put his affairs in order and concocted a plan to travel to Deep Space Nine posing as Gul Darhe'el and have himself put on trial as a war criminal. This, he believed, would force the Cardassian Union to own up to its crimes on Bajor.
But for the suspicions of station security chief Odo, his plan may very well have succeeded. As it turned out, not only was the true Butcher of Gallitep dead, but he had not been present at the camp on the day of the mining accident that gave Marritza Kalla-Nohra syndrome.
In light of this discovery, Marritza was released for return to Kora II, where the authorities told DS9 officials they intended to help Marritza reintegrate into life there. Before he made it off the station, however, Marritza was killed by a Bajoran--not because he was Gul Darhe'el, but because he was a Cardassian.
In an alternate reality where Cardassia was occupied rather than Bajor, Aamin Marritza lived on Cardassia Prime. The Bajoran occupiers identified Marritza's eye for detail and put him in a stoneworkers' crew whose job it was to build the mosaics the Bajorans used in their temples for Pah-Wraith worship.
Marritza carried out this work as of 2351 with no outward signs of complaint, and did what he could to aid other team members in completing their assignments without mistakes that could cost them what little remained of their well-being and their lives. What the Bajorans did not realize was that they had assigned an Oralian Guide--one of the Cardassian clergy--to this task, one who took his work as an act of spiritual sabotage against the Pah-Wraiths.
Marritza's vocation as a Guide (a rare profession for a man, in the Oralian faith) owed in part to his extreme sensitivity to the emotions of others. Prolonged eye contact or the intense scrutiny of others, be they Cardassian or Bajoran, could cause him to experience vivid echoes of their sufferings. He was also known to have visions on occasion. As a Guide, however, Marritza had a way to put his gift/curse to use and to cope with the spiritual fallout of his abilities.
Due to the Bajoran persecution of the Oralian faith, Marritza could not serve openly in his role as Guide. Services had to be conducted in secret with his face hidden from view, except around a few prominent members of the Resistance who knew his identity. One of these was Skrain Dukat, to whom Marritza would minister following the Resistance leader's capture and torture on Bajor. (Sigils and Unions: Catacombs of Oralius--"The Guide")