The army was led (of course) by the Lord Castellan Usarkar Creed, snatched from the fall of Cadia at the last second, along with a squad from his beloved Cadian 8th Regiment.
Also from the Cadian 8th, a Devil Dog tank for support that was heavily damaged during the battle, and has been undergoing meticulous repairs since then by Trazyn's scarabs.
Of course, Trazyn the Infinite would never be satisfied with only one regiment, so he also collected a squad of the Tanith 2nd Regiment, previously thought to have been destroyed along with their homeworld, but rescued by Trazyn in his quest for unique exhibits. I used the Borderworld Rangers models from Victoria Miniatures as the base for the Tanith, I think they're a pretty good match for the light infantry style of the Tanith.
Next up is probably my favorite piece in Trazyn's collection: Maximilian Weisemann. Originally described in Imperial Armour 1, Weisemann was the commander of the Baneblade 212 Arethusa who led a one tank assault against an ork army to buy time for the Imperial battle line. Though his tank was destroyed, Weisemann himself was never found on the battlefield. Not being one particularly interested in historical accuracy, Trazyn has faithfully recreated the 212 Arethusa for Weisemann to command - as a Leman Russ Punisher. I converted a Cadian tank commander model to match the old Maximilian Weisemann model (long since out of print).
Finally, rounding out the army was a unit of storm troopers from the retinue of Inquisitor Valeria that were captured during her assault on the Solemnace galleries, and a unit of the Vostroyan XXI, a long lost Vostroyan regiment that was noted to be in Trazyn's collection during the Gathering Storm event.