Yes it was Castle Netvill that had the griffins in my game. I had forgotten that you can get more from the Griffin king - completely forgotten about that. There's so much to do in this game that you can't remember everything (this is why we need a search function). I loved using the griffins but I ran out of places to get them so I moved on to other units.
I also LOVE royal snakes. Is there somewhere that has an unlimited supply? One of the castles in Marshan Swamp had a lot (maybe 600) but they ran out eventually.