See Challenge # 154.

Magic Sphinxes usually have flying, but I think the flavour concept doesn't need it, so if we're starting over, if sphinxes go in red, maybe they don't. Not sure what happens if sphinxes are mostly white.

Lots of people try "guess a spell" mechanics, and it's hard to do right. Doubtful I managed it here.

Two key points. One is, during combat, there's a much narrower selection, so it's more plausible to guess. The other is, you guess before the card is chosen, ie. before costs, so there's no awkward rewinding.

The other is how the rules works. I think it works like this. If opponent screws up and eg. has no valid targets and needs to rewind, that only benefits you by knowing what the card is after you guessed wrong. If you guess right, they don't get as far as paying costs or choosing targets.

That's kind of weird I guess. I see the idea, but I feel the implementation is awkward on the card.

During the combat phase, opponents exile spells without revealing them before casting them. You may guess the name of each spell exiled this way. If you guessed correctly, that spell can't be cast, otherwise the spell may be cast.

There's probably still a bunch of things wrong with that.

The ability also feels blue, mainly since the combat phase will most likely be seeing instants, which seem more like something blue is going to counter. I don't know how many things with flash would be in the opposing deck, but I'm not imagining too many that it'd be white's concern. I really like the idea, but main phase would feel more white to me.

I think an "exile first" version might be better, but I wasn't sure I could get the rules to work.