Oracle of Mul Daya
I don’t know the odds of getting this broken 4-drop, but I do know the approximate odds of you winning if you do: 100%. You may not realize it, but this is a winning board state almost (99.9999%?) every time:
Momir is defined by a simple rule: at some point, you must balance whether to discard or play a land. For that reason, players must choose between developing their board or creating larger minions. Oracle of Mul Daya breaks that rule by allowing land drops from the deck. And then breaks the rule even more by allowing for mana acceleration. Dropping 10-cost creatures when your opponent is dropping 6-cost is likely to win the game. Not to mention always having the mana to pay for creature ability costs.
Bouncing multiple creatures is an excellent way to break up a board stall.
Then again, this card screams for you to slam 9-mana Momir activations. My opponent dropped this one on me, and had me looking for the best CMC for getting rid of pesky creatures. I think the answer here is 7 (Meteor Golem).
This may seem underwhelming, but Momir is all about trying to find a way to break parity.