Thassa's Oracle

The alternative win condition that finally made the "mill yourself out and win" plan safe. Older library-empty payoffs came with a fatal delay: Laboratory Maniac replaced your fatal draw only if you lived to draw at all, which meant surviving a full turn cycle with your deck at zero and an opponent free to disrupt you. This closes that window by checking on the enters trigger itself, comparing your devotion to blue against the cards left in your library and winning immediately if the count clears. Empty your library first, cast it, and the game is over on resolution rather than three turns later. What keeps the door open for opponents is that the win still lives on the stack: it is a triggered ability, so they get priority in response, and a Stifle or an instant-speed draw effect that changes your library size can pull the win out from under you. That single change (the check happening on entry instead of on your next draw step) rewrote the cheat-your-deck-empty archetype from a fragile durdle into a real combo, since the payoff just wins with an empty library behind it. The devotion clause keeps it fair everywhere else: without that empty library you are digging only a few cards deep, so the card is a dead draw in ordinary games and a guaranteed win in the exact spot the deck is built to reach. That knife-edge is why it lives permanently in eternal-format combo and surfaces in ban discussions wherever the go-off gets too easy to assemble.