Evolving Door

Most tutors ask you to pay in mana or life; this one asks you to pay in color. The engine counts the colors of whatever creature you sacrifice, then fetches a creature with exactly one more color, which turns a plane's chromatic gradient into a literal search staircase: a mono-colored dork finds a two-color body, that two-color body finds a three-color midrange piece, and so on up the ladder toward whatever four- or five-color payoff sits at the top. Note that it counts colors, not color identity: a mono-green creature packing an off-color activated ability still reads as one color here, so the rung it fetches is decided by the mana symbols in the card's cost, not its rules text. That climbing structure is the whole design idea, and it is also the constraint: each activation costs a creature of a specific hue-count, so you cannot skip a rung, and the sorcery-speed clause plus the exile-and-cast wording keep it from doubling as instant-speed interaction or a graveyard loop. The counting rule rewards a roster that spans the spectrum rather than any single color, which makes it an oddly specific artifact: it wants a creature at every step, from mono to WUBRG, and stalls in a two-color shell that lacks the intermediate links. What it represents is a tutor that measures a deck's color spread as the resource, a mechanic that only makes sense on a plane built around chromatic factions.