Im not convinced that picking up a Force of Negation can have the same impact on controlling the early-game and buying back an Opt doesnt hit the same when my opponents are just killing me on Turn 2
I stipulated blue in the title, this was merely so I didn't have to work out where Mana Tithe fits into the mix and spend a lot of convoluted time discussing the implications of a functional reprint in a different colour
For each of those cards, pay 4 life or put the card on top of your library. Effectively, its a bit like Brainstorm, but on every turn
You may pay the entry and rejoin to select new packets and play again
This cross-Guild synergy should be good, but in practice, it makes playing both guilds rather same-y as both guilds encourage playing below-rate creatures that mandate minimizing the number of noncreature spells in your deck
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