Thunder Hammer Indomitus Terminator

I wanted to get my hands on the new plastic terminators for 40k from when I first saw them. They looked brilliant. But my plans for them are categorically not for 40k - they are for 30k and the Horus Heresy. The Indomitus Terminator mark should only really be taken for the thunder hammer and storm shield combination or the proteus assault cannon (as I discuss in the 30k review article). So here's the first terminator of the squad. 

Just a head swap here wherein I have replaced the standard head with a traitorous chaos space marine terminator head. 

The main question is really: what legion will this become?!