mtg cards like dockside extortionist where X is the number of artifacts and enchantments your opponents control The best dockside replacement extortionist

The probability analysis is the best of any deck builder I've tested

The other two are fantastic as well

Ur-Dragon has a rebate, which means that this would be able to return a dragon that cost you just 2 mana to play, unless you use backup on itself

Grab two boosters, shuffle them together, and you're ready to go

2 Karumonix, The Rat King Toxic Rats While Karumonix, the Rat King, is a solid commander in its own right, it's much better used in the 99 since other commanders can make Rats quickly that Karumonix can back up

Having a full extra turn to play your cards - on top of a Flashback cost that mitigates paying for the spells you exile - pushes this into the realm of being a red staple