Besides immortality and Ritual of Rebirth, it seems that Ritual of Returning works too. Orokestes was in the home citadel of Arcos when I attacked and got him, I don't think he died. Arcos died on the same turn. I got that devil to my home province of Pangaea.
I have the save file (of the turn it has happened) in case you need it, but it's Dom:PPP.
BTW, I almost made a really bad typo in this post. "Besides imorality and Ritual of... "
EDIT: Oops, "rituals like Ritual of Rebirth"... not RoR alone.
[ April 25, 2004, 12:12: Message edited by: Endoperez ]