Scoria Wurm - Not that exciting, but its a cheap threat that you could hopefully keep alive longer with Krark's Thumb Mirror March - This can get out of hand really quickly, and there's basically no downside to losing flips Yusri, Fortune's Flame - Designed to be a commander, but it's a solid card to include in the 99 as well Goblin Traprunner - Tons of easy flips with no downsides Squee's Revenge - Can be a huge card draw Planar Chaos - This one can be a bit annoying and might only be good if you also have Krark's Thumb, but it lets you play more controlling Krark, the Thumbless - Similar to Planar Chaos, use at your own risk Frenetic Efreet and Frenetic Sliver - A single card that lets you flip as many coins as you want (you can activate the ability as many times as you want before you let any of the activations resolve, and then even if he dies you still flip all the coins) Puppet's Verdict - A sweeper that let's you control what to kill if you can manipulate the flip As for other cards that I think could fit the strategy of the deck, I would focus on ways to multiply your other effects (extra upkeep steps, copying your permanents, doubling your abilities, etc)

It rocks card-draw, discard, and more
Blasphemous Act Blasphemous Act is the quintessential red creature board wipe that can turn into a 1-drop as long as there are eight or more creatures total on the battlefield
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You can continuously use this to kill the creature
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