North of the castle that will be the spawn point, there is a small wooden house in the middle of a frozen lake. Inside, you'll find a mineshaft. This mineshaft is to collect stone to make a Free-To-Take mob system, the design of which is here:
http://www.youtube.com/watch?v=jfS_Y0mPA40
Once we have 45000 stone, (Oxifire) will begin this construction. If you all want all the mob drops you can handle, please mine here and leave me your stone!
Oh, did I forget to mention the best part? You can keep anything you find down there other than stone! Even diamond! I just would like your stone, please.