Evolving Door
Artifact
, 
, Sacrifice a creature: Count the colors of the sacrificed creature, then search your library for a creature card that's exactly that many colors plus one. Exile that card, then shuffle. You may cast the exiled card. Activate only as a sorcery.
In with the old, out with the new.
Drew Baker
Rulings
You count the colors of the sacrificed creature as it last existed on the battlefield. Notably, if it was a double-faced card or a copy of another creature, that may be different from what its colors are in the graveyard.
(wotc • 2022-04-29)
If you choose to cast the spell, you must cast it as Evolving Door's ability resolves. You cannot wait and cast it later.
(wotc • 2022-04-29)
You must pay all costs for a spell you cast this way.
(wotc • 2022-04-29)
Evolving Door's ability instructs you to count the number of colors, but it doesn't track what those colors were. For example, if you sacrifice a creature that is green and no other colors, you'll search for any creature card that is exactly two colors, even if the card you search for isn't green.
(wotc • 2022-04-29)
If you sacrifice a colorless creature, you must search your library for a creature card with exactly one color. If you sacrifice a creature that is all five colors, you won't be able to find any creatures because there are no creature cards in Magic with six colors.
(wotc • 2022-04-29)
Rulings
You count the colors of the sacrificed creature as it last existed on the battlefield. Notably, if it was a double-faced card or a copy of another creature, that may be different from what its colors are in the graveyard.
(wotc • 2022-04-29)
If you choose to cast the spell, you must cast it as Evolving Door's ability resolves. You cannot wait and cast it later.
(wotc • 2022-04-29)
You must pay all costs for a spell you cast this way.
(wotc • 2022-04-29)
Evolving Door's ability instructs you to count the number of colors, but it doesn't track what those colors were. For example, if you sacrifice a creature that is green and no other colors, you'll search for any creature card that is exactly two colors, even if the card you search for isn't green.
(wotc • 2022-04-29)
If you sacrifice a colorless creature, you must search your library for a creature card with exactly one color. If you sacrifice a creature that is all five colors, you won't be able to find any creatures because there are no creature cards in Magic with six colors.
(wotc • 2022-04-29)