Here's the fluff for him -
Thanks to Cholothrax's successful alliance with the Skaven of Clan Festerscar, the Rotbringers were experiencing success after success in the Realm of Beasts. Cholophract remembered his time serving under Cholothrax before his disappearance. He often wondered what had happened to his brother after he followed the Prophet through the Rot Tree and if he'd live long enough to see him again...
Cholophract and the other leaders of the Rotbringers were close to figuring out the correct ritual to traversing the Rot Tree, being able to use it in the manner of a regular realm gate, and when the moment came, he would mount an expedition into the other realms to find Cholothrax...
I'm now focused on the next Rise of Empires narrative campaign, and will be rolling up a Free Peoples army using the Path to Glory tables beginning in September! I'll also try to post up about my Renegade Guard progress at some point!