Like countermagic, they offer an alternate route of resource denial that strips your opponents of cards before they hit the table
You can't just weave these into any of our products, but when you're doing these one-off cards and you're trying to build a Chun-Li that's gonna go on to live a wonderful life in Commander decks where people are pulling through all of Magic, it just unlocks all of that. Heggen says that Commander is the primary lens through which [were] viewing these, but that theres no arbitrary threshold they have to hit in terms of viability or popularity in the format
He once managed to put Elesh Norn, Grand Cenobite into play and then copy it with Sakashima the Impostor and I still haven't forgiven him for it
But you sure do sacrifice a Solemn Simulacrum to get a Sword of X and Y back, and you do it in Cube any time you can
I havent noticed many lifegain decks running around recently, at least not in Standard, but they do exist in abundance in Pioneer and Explorer, so it might be intended for those formats
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