­Disembowel? + Slime Molding

Guess I'm making an X spell then.

In fact we kinda have the most-black X spell and the most green X spell ever. (La la la Stream of Life and Drain Life cannot hear you.)

Huh. Red had Fireball and Disintegrate. Blue obviously had Spell Blast and Power Sink. What did white have in X? ... no, Nine-Tail White Fox is not relevant, thank you very much card search, you so broken right now.

So by process of "My memory of alpha is flaky" a white X spell.

Hmm, what's white primary in right now? -X/+X? That could be a thing, though it's kinda 'prevent X damage' (which white can also do of course).

I think we'll go with the more useful tapdown. I don't see "tap X creatures" has been printed yet? Ah, "tap X target creatures". And it's Glimpse the Sun God. Phooey.

Ok, back to ...Belbe's Armor. As an instant. Bah. "Belb" is a verb for this effect now. (HOW is white officially primary in an effect that isn't actually on any printed white cards?)

...ok, finally managed to find it. White's X spell was Guardian Angel. Which is kinda interesting, since it's not just 'prevent X damage' but is also 'and I can keep paying more if you keep trying to damage it this turn'. (Which is, of course, why it got removed in 4th; because actually templating that in real rules is even nastier than regeneration)