Tartarus is an icy inferno.

Interesting faction, I really like it :) The atmosphere is well-maintained (in my opinion, the most important thing in a faction is the atmosphere and the harmonious combination of units), and the idea and history of the faction are interesting. Everything is wonderful, keep it up ;)
P.S. In my opinion, if you're going to change one of the castles to Tartarus, then it should be Inferno ;)