Isirvia, Motherly Trickster

Spectacle {3}{b}{r} (You may cast this spell for its
spectacle cost rather than its mana cost if an
opponent lost life this turn.)
When Isirvia, Motherly Trickster, enters the
battlefield, sacrifice a legendary creature you
control, then search your library for a legendary
creature with converted mana cost equal or lower
to the cost of the sacrificed creature, and bring it
into play, then shuffle your library.