Big Priest loses Barnes and a lot of board clearing mechanisms in the rotation, so this list will probably be bad, but there’s still more Priest cards to be revealed so who knows! The main idea here is that Dragonhatcher functions as a much worse Y’shaarj. Sleepy Dragon was chosen over Obsidian Statue because it gets recruited. Malygos is here for pretty obvious reasons. Free From Amber gives you some late game flexibility, though it may not synergize well with Lesser Diamond Spellstone since you ideally want to bring back Malygos.
I don’t expect a deck like this to be good, but it might be fun!