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Although I like this, because it works with a seldomly used space, I have no idea how this would work. Might also lead to unfun games if a player can't build the deck they want to build.

This card is designed for a cube, a Limited environment. You are always dependent on the cards you open and by default cannot "build the deck you want".

What I mean is this: Usually, a game is best of 3, so if you lose the first game and Hurl into Blind Eternities was used on a card my deck was focused around, well, tough luck, my deck is kind of ruined now. And if it was the first match I have played altogether all the subsequent games are going to be unfun as well, at least if everybody is going to play against everybody else and it isn't an elimination style tournament.

Don't get me wrong, I think this could be fun if everybody's on board with an effect like this, but I know I wouldn't like it if a single card ruined my weird combo deck I tried to build.

I think the equivalent place to be looking is the old ante cards. And apart from the truly obscenely broken ones - they mostly came with downside.

I suggest that this card also really-freakin-removed-from-the-game-forever itself. (Also, very very nice flavour you've come up with for that zone.)