Ydrael of the Lost Path

When Ydrael of the Lost Path enteres the battlefield, search your library for a card.
Exile it under Ydrael of the Lost Path. Whenever Ydrael of the Lost Path leaves
the battlefield or you're dealt demage equal
or less then the converted mana cost of the
card exiled with Ydrael of the Lost Path,
you may cast that card from exile without
paying it's mana cost.