The Sons of Tain was the name of an unofficial group that operated within the Obsidian Order of the Cardassian Union.
Overview[]
This organization rose to prominence in the year 2347 when Enabran Tain began his rise within the Order as its head. With his ascendance into power, he began taking number of Cardassian agents under his tutelage who were given one of his "Sons". This gave them a great level of personal power within the Order and all that mattered was what Tain thought of them. (DS9 novel: Night of the Wolves)
Many members of the Obsidian Order feared and resented Elim Garak for being one of the "Sons of Tain", although Garak knew Corbin Entek to not be one of them. (DS9 novel: A Stitch in Time)