In the case of the Opportunist, you basically get a delayed copy of the second spell you cast in a given turn
Whenever it or another Ally enters, you can essentially scry the top four cards of your library, and put any Ally cards you find back on top while the rest go to the bottom (although, you can choose to put Ally cards on the bottom as well if you don't reveal)
1 Omnath, Locus of All
While it takes more work to spin, the Academy Rector is just as bad, because it's not card disadvantage or with a counter-able sacrifice effect
Heres what those memorable episodes do for you in-game: The City on the Edge of Forever (White/Black) 1: All artifacts and creatures phase out
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