I feel that the reason they don't run clone is that it isn't as good as the answers that they already use. I mean O ring and dodge are better answers to emrakul and Iona on blue. They already use both of those to deal with creatures and in o rings case as a catch all card.. Jace the Mind Sculpter also answers Emrakul and it answers Iona on white. They also already have sideboard counter magic which will help at least slow down polymorph while being good in the mirror while clone is only good against polymorph.
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Mycosynth Lattice, March of the Machines, Experiment Kraj, and a planeswaker of your choice.
They changed the planeswalker rules so this no longer lets kraj use their abilities an infinite number of times.
One of the things that this block currently lacks is evasive tokens. Both the spectral procession tokens and the bitterblossom tokens flew which made them harder to just block. The spawn tokens also start out at zero power so they aren't at all aggresive by themselves. Another difference is that a glorious anthem for all your tokens costs more to cast then it did then. We also currently lack manlands that can swing as quickly as mutavault could. We also do not have the powerful windbrisk heights interaction.
I think that if I had to choose one, it would be the prism because your early plays make a lot of difference against that deck so having your spells available earlier is very important.
I think that there are probably not enough cards to make a strategy like this work because they are all to slow and there is not an inexpensive way to put a chosen creature into your graveyard. That said if you are set on trying, it may be beneficial to look into an artifact strategy with steal wind as the big creature which can be brought back by sharuum the hegemon. Although open the vaults may still be a better deck idea.
I currently think that the angel is not really worth playing because it provides the same amount of pressure as other win conditions as far as damage while being easier to kill. I mean, the ability makes it indestructible which is pretty good, but for it to have that protection it means you need 8 mana. I would much rather use 9 for iona and just lock them most of the way out. At its regular price it is destroyed by a lot more than sphinx of jwar isle while it doesn't provide the same edge in a race as baneslayer does.
I think that at least kozilek will see play because there is already a deck that can consistently cast him in the form of UW control. I feel that it will see play there simply because it already gains additional card advantage. I feel that it has a shot against Iona simply because it provides more of a board presence. The reason I feel that way is it is harder to race it with what is already on the board. However, I do acknowledge that Iona is much better protected.
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Mycosynth Lattice, March of the Machines, Experiment Kraj, and a planeswaker of your choice.
They changed the planeswalker rules so this no longer lets kraj use their abilities an infinite number of times.