This is definitely a mythic rare, and probably undercosted. Unfortunately, it can feel horribly bad when you suddenly lose to a spell, which is why alternate victories tend to be from upkeep triggers on permanents. On the other hand, Coalition Victory shows us that it's printable, and the flavor of your world requires that it be a sorcery. The good news is that instant-speed creature removal can still disrupt it, so it's not entirely noninteractive.

Yeah, this is a huge example of "If you haven't read the spoilers, you just lose now, thanks, with no idea it is coming."

It really needs to have some kind of countdown.

Hmm. Well I could make it an enchantment, like the other alternate win conditions, but it's black, and black in this set is sorceries (and instants). An enchantment should be green (or white). But I guess you're right.

For flavour it really does want to be a Sorcery. How about "At the beginning of the next end step, if..."?

I wondered about that. But that wording really, really seems like "I want to be an enchantment, I'm just being hacked into sorcery form".

I see the problem. It's possible to a) say that some black cards should be enchantments, like some black cards are instants b) make it do something overwhelming but not outright winning, or otherwise contingent c) tweak the mechanics so it does aproximately the same thing but feels like a sorcery. I debated alternatives for c), but nothing seemed perfect.

"At the next end step" wouldn't quite be an enchantment as it would only happen once, but I agree it's not quite a sorcery. The same would apply to having the sorcery work or be cast from the graveyard.

Hmm. There's some possibility in letting it be cast from a graveyard. Something like "Discard any number of cards from your hand. // You may cast ~ from your graveyard if you didn't cast a spell named ~ this turn. If it was cast from a graveyard, you win the game if you have blah blah." It's nowhere near as elegant though.

Yeah. I was thinking of "if ~ is in your graveyard at the beginning of your upkeep, win the game if..." but I can't think of any good wording.

Of if it can't be a sorcery or an enchantment, maybe it could be a creature or an artifact?

Artifacts are just as out as enchantments, in this set, for the same reason. Creature is an interesting idea. I don't think there's been an alternate win condition creature before. But I can't help feeling it would still make people go "But shouldn't the black-red sorcery group's alt-win card be a sorcery?"

I think my options are 1) Decide it's okay as a sorcery after all - decide that Coalition Victory wasn't that bad. Unfortunately dismisses V's original problem. 2) Kill this card, and possibly consider designing a green or white alt-win enchantment for this set instead. Painful, but I fear it may be the best option.

"If you have at least ... graveyard and if you told your opponent during the previous turn that you have this card in your deck, win the game." :) I have the disability of being unable to distinguish between helpful suggestions and tongue-in-cheek ones, which mean all my brainstorming is very... random :)

I agree you probably have to pick one of those, and that it will probably be fine whichever you do. After all, it's been long enough you can hopefully let the card go without too much of a wrench if you decide you need to.

OTOH, I don't really see people saying "shouldn't it be a sorcery" if it were a creature. I think the design logic is sufficiently removed from the end result that people won't think like that, or at any rate, it wouldn't have occurred to me. In fact, I like this idea more now.

"I don't think there's been an alternate win condition creature before."

See Felidar Sovereign.

Mmm. Good points, and yes, of course Felidar Sovereign. Okay, then, perhaps a creature (a Legendary cardinal) is the way to do this. Thanks all.