You can only activate this card when your opponent activates a card that specifically designates a monster in the Graveyard as a target. Remove all monsters in both players' Graveyards from play.
With the current format taking great use of the graveyard, this little trap can shine. Even though most don't consider it due to the risk or removing their own monsters, decks that don't require much graveyard use can take full advantage of this...
So to name a few...
Macro, Glads, Anti-Meta Gadgets, Rock Stun
This card is in my main deck for KillSwitch and it's incredible.
Opponent summons Ragigura and targets his Faultroll, or activates Gottom's E-Call to revive 2 Sabers...Big Burn solves the problem!
Your opponent has just summoned Infernity Necromancer and targets Archfiend, Big Burn!
By having it main decked, it is sure to give a surprise at game 1, along with quite the advantage.