S.L.O.W. introductions Kristl.

This is just my opinion, but I feel it should not be Thor who should be the one put in the bathroom, but the rescue kitty. Don't forget, this is Thor's home. By you locking Thor in the bathroom it will make him reject the new addition.

Put Angel in the bathroom for the time being. Rub her with a towel to get her scent and then place it on the floor in the room where your cats are. This way they will get use to her scent and also do the same with your cats and place it in the bathroom so Angel can get use to your cats scent.

I always introduced my new additions, by placing them in a cat carrier and placing them in the middle of a room for about half an hour so the others could investigate the new one. Expect some hissing and growling going on. Then put the new one back in the room. I did this for a few days and then left the carrier out longer as time went on. After about a week and a half, I placed the carrier in the middle of the room and left the door open.
Fortunately it went well for me.

I'm sure others with have other suggestions also.

Good luck in whatever you decide to do.