thats very late, and u mgith aswell googled it out, but Im bored so:
it destroys all creatures (undepended of their owners) which can save you from a quick death against a lot of small size creatures. In addition it lets you search your opponents library for 3 additional creatures and put them in his graveyard. Which, considering the rather high mana costs will be at a point where you know his most dangerous creatures and therefor prevent him from regaining strength. However considering the cards mana costs its more of a get a last chance thing than a real tactic.