This is the best card for a Dark World Deck's Side Deck, because you can destroy cards that hold back your Dark World Monsters. Ex. "Gravity Bind", "Level Limit - Area B", and other cards that stall.
This card works very well with "Depth Amulet", in that you can negate an attack, as well as destroy a spell/ trap card. This combo also works well with "Kahkki, Guerilla of Dark World".
Note that this card's effect is mandatory: if it's discarded to the Graveyard, you HAVE to destroy one spell/trap card on the field. If your opponent does not control any, you are obliged to target one of your own.