the singleton iona's a dread return target, i'd never be able to hardcast her. in theory a turn 2/3 iona shuts down most decks, especially if you know what color their removal is in. wild mongrel is interesting.  this is my first build with cephalid coliseum, so i'm accustomed to only playing one land for the entirety of the game.  having access to more mana might open up other possibilities.  tribe is cool though cause it blocks all day long without sending opp's creatures to the yard (which would cost me my bridges).  btw, thanks for reading and commenting.

Personally I would drop the heavy white Iona.. swap the tireless tribe for the Wild Mongrel... I'd play something that just WINS with you return it... Iona is ok... But why not just go eldrazi or some fat titan 

It's like a threshold deck merged with dredge.. I donno if it would work :)  Interested to see though.