Degeneration Chamber

{1}{g}, {t}, Sacrifice a creature: Search your library for a creature card with converted mana cost equal to sacrificed creature's converted mana cost minus 1, put that card onto the battlefield, then shuffle your library.
"'Only through knowing our past selves can we understand our future selves.' Obviously this applies to our biology as well as our personalities. Why don't we take a look at what once made us tick?"