It looks to use a Cadian head and a CSM top knot. I am not sure where the hammer is from, but I think even a normal stormcast hammer would be fine.
Really awesome concept and execution. I am planning on doing the same for some proxy TH&SS Terminators.
But it also got me thinking, what if we made some Warscrolls for battles in the Age of Unity. The Mechanics of the AoS game would support this IMO. Thunderwarriors vs Ursh, the Yndonesian Bloc vs Hy Brasil. Could be alot of fun. I would just remove all summoning from that game.
