Enigma Sphinx
Artifact Creature — Sphinx
Oracle Text
Flying
When this creature is put into your graveyard from the battlefield, put it into your library third from the top.
Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)
Watch Out
This triggers when the spell is cast, before it resolves. Even if the spell is countered, the cast trigger still resolves. Copies of spells are not cast, so they won't trigger this.
'Dies' means 'put into a graveyard from the battlefield.' If a creature is exiled instead of dying (Swords to Plowshares, Rest in Peace), dies triggers won't fire. Tokens do trigger 'dies' abilities briefly before ceasing to exist.