Wording:

Flip Cavendish Hall only if you control a Thule Society character.

Crossover Thule Society and B.P.R.D.

Activate >>> Target attacker or defender you control gets +1 DEF this attack.

Now the way this is worded, I don't have to control BPRD to team them up.. only Thule must be controlled..

Now correct me if I'm wrong as they might have errata'd and/or clarified, but if this does ondeed work then I might have a very good Project Ragna Rok deck. I'll post the idea after I figure out if this actually legal..

Yep. You only need Thule Society.

Kool only problem now is that I didn't realize Ragna Rok was only once per turn so my idea doesn't really work anyway..

Well with the lil army guys you could easily win on turn 4 if that were the case lol