I don't do the adventures hoping for the prize, I do them for the other drops. I was able to finish today because of the Ivy items dropped from adventures. If I get the prize it's just a pleasant...
They spawn from cows (but check you have no other monsters on your board)
The fangbeasts remind me of Nanny McFee. (When you want me I'll not be there but when you don't want me I will be there...