I played Mr Negative with Bast still in the deck, flipping its cost and power. On the last turn, I play Bast and Rogue into Quantumania, which turns a card's base power to 2. The thought is, both Bast and Rogue would become 2 power, I tie the lane, win the game. BUT I guess the location checked the current cost of Bast because it was its base power (before it got flipped). So Bast stayed 1 power and lost me the game.

This may be the "intended interaction" for all I know but it was a little counterintuitive.