Oh Jesus, I wandered into a cluster fuck . . .
So, I've read through what's going on.
I'm not pulling favorites, but apparently Mike and Lantz have had something planned for the Castle for a long time. Just suddenly dropping a fallen angel could fuck up their plans. Not to mention, Magos, you're going to have to wait for Lantz to respond, and he and Mike are working on . . . something.
If you wanted to have Raul interact with someone, what about Downy Reed and his summoning circle of Doom?
Or, Lantz, since I'm slightly familiar with how WoD works, technically, considering what Raul is, he may be able to get into the castle undetected. Guy is a fallen angel. He wouldn't be say Arc or Gil tier, but he'd have a high enough mystery to fuck up a Servant. Plus they can manipulate reality around them- that's one of the game's rules.
Considering this, Raul doesn't have to bust up random guard 878. He could just be wandering around the castle until shit goes down.