Zendikar — Rare
Creature — Merfolk Wizard
Cosi's Trickster rulings:
10/1/2009 : Cosi’s Trickster’s ability triggers when an opponent shuffles his or her library because that player was instructed to do so by a spell or ability that specifically contains the word “shuffle” in its text or (in the case of a keyword ability) in its rules.
10/1/2009 : The cascade ability doesn’t cause a player to shuffle his or her library, even if that player revealed his or her entire library. The revealed cards are put on the bottom of their owner’s library in a random order, but they’re not “shuffled.”
10/1/2009 : If an opponent’s library is empty or has just a single card in it when a spell or ability instructs that player to shuffle his or her library, Cosi’s Trickster’s ability will still trigger.