So the dimension is yours, but the building isn't. So you claim, at the very least. What do you normally use this dimension for, in that case?

[ and how do you just 'accidentally' an entire castle and the surrounding grounds into it out of nowhere? ]

And as for our abilities... [ what an interesting thing to say. would he? ] A side effect of whatever spell it was you were trying to cast? Or did you simply not want to be threatened by anyone who might or might not hold more power than you?