As an additional cost to cast this spell, sacrifice a creature.
Search your library for a creature card with converted mana cost X or less, where X is 2 plus the sacrificed creature's converted mana cost. Put that card onto the battlefield, then shuffle your library. Exile Eldritch Evolution.
7/13/2016 Sacrificing 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.
7/13/2016 Once 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.
7/13/2016 A creature’s converted mana cost 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 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 converted mana cost is 0. Ignore any alternative costs or additional costs (such as kicker) paid when the creature was cast.
7/13/2016 A token that isn’t a copy of another permanent has a converted mana cost of 0. A token that is a copy or a creature that has become a copy of another permanent has the converted mana cost of what it’s copying.
7/13/2016 The converted mana cost of a permanent that’s a double-faced card with its back face up is the converted mana cost of its front face. The converted mana cost of a melded permanent is the sum of the converted mana costs of its front faces. A creature that’s a copy of either has a converted mana cost of 0.
7/13/2016 If a card in a library has 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 .