They can be particularly powerful with counterspells, which I imagine is the pair here, because treasures allow you to tap out while still holding up a counter
If Betrayer's Bargain resolves, its effect causes the creature to be exiled any time it would die that turn, not just if it would die as a result of damage dealt by Betrayer's Bargain
With no downsides and a host of useful attributes, youll never want to skip an opening hand that includes Ragavan
Youll much prefer the emblem on Nissa, Vital Force instead, so well replace one with the other and not help the other three players at the table quite so much
Then Magic Academy events at your local game store are perfect for you
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