He was the father of Elim Garak. However, he was illegitimate and Tain never told him that he was his son. He despised the Terran Rebellion for its role in Garak's death and for denying him the opportunity to forge a relationship with him.
In 2378, he commanded an Obsidian Order fleet, the existence of which was hidden from Central Command, and led it in support of the renegade Klingon Krona's attempt to destroy Bajor's sun B'hava'el using a trilithium explosive. Although it seemed highly likely that Tain's fleet would destroy the joint Terran Rebellion / Memory Omega forces, the Obsidian Orders ships were destroyed with all hands by the extremely powerful Ocampa telepath Kes using her psionic abilities. (ST - Mirror Universe novel: Rise Like Lions)
Dark Passions continuityEdit
In another permutation of the mirror universe, he was the director of the Cardassian Obsidian Order during the 2350s and 2360s. Tain saw the worth of young Annika Hansen in 2355 and inducted her into the Order when she was rejected by Ghemor. In 2369, he ordered Annika to assassinate Duras on Khitomer before the Cardassian delegation arrived to a conference there. (ST novel: Dark Passions, Book One)