FOILCheapest priced copy (Innistrad Remastered): $4.99 at Card Kingdom, near mint, their price list as of .
Eldritch Evolution 
Sorcery · Rare · Eldritch Moon Promos · #155s
As an additional cost to cast this spell, sacrifice a creature.
Search your library for a creature card with mana value X or less, where X is 2 plus the sacrificed creature's mana value. Put that card onto the battlefield, then shuffle. Exile Eldritch Evolution.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
7 printings · $4.99 to $44.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Eldritch Moon | 155 | Rare | $5.99 | $9.99Out of stock |
| Innistrad Remastered | 195 | Rare | $4.99 | $6.99 |
| Innistrad Remastered | 410 | Rare | $5.49 | $9.99 |
| Eldritch Moon Promos | 155s | Rare | — | $10.99 |
| The List | EMN-155 | Rare | $4.99 | — |
| Secret Lair Drop | 1414 | Rare | $20.99 | $21.99Out of stock |
| Secret Lair Promo | 5 | Rare | $11.99 | $44.99 |
6 rulings from Wizards of the Coast
- 13 July 2016Sacrificing a creature is part of Eldritch Evolution's cost. You can't sacrifice more creatures to search for more creature cards, and you can't cast Eldritch Evolution at all if you control no creatures.
- 13 July 2016If a card in a library has {X} in its mana cost, X is considered to be 0. If you find such a card this way, you won't have an opportunity to spend mana on {X}.
- 13 July 2016The mana value of a permanent that's a double-faced card with its back face up is the mana value of its front face. The mana value of a melded permanent is the sum of the mana values of its front faces. A creature that's a copy of either has a mana value of 0.
- 13 July 2016A token that isn't a copy of another permanent has a mana value of 0. A token that is a copy or a creature that has become a copy of another permanent has the mana value of what it's copying.
- 13 July 2016A creature's mana value is determined solely by the mana symbols printed in its upper right corner (unless that creature is the back face of a double-faced card, a melded card, or is copying something else; see below). If the mana cost includes {X}, X is considered to be 0. If it's a single-faced card with no mana symbols in its upper right corner (because it's an animated land, for example), its mana value is 0. Ignore any alternative costs or additional costs (such as kicker) paid when the creature was cast.
- 13 July 2016Once you begin to cast Eldritch Evolution, no player may take actions until you're done. Notably, opponents can't try to remove the creature you wish to sacrifice.