It's Been Done Before

Recently I've been hearing players begin discussing what to side in against Dark Worlds once Structure Deck: Gates of the Underworld reaches the TCG. The most commonly suggested solution is:

Gemini Imps

(Fiend-Type/DARK/Level 4/ATK 1000/DEF 1000)

"When a card effect controlled by your opponent is activated which would cause you to discard from your hand, by sending this card from your hand to the Graveyard, negate the activation and the effect of the card and destroy it. Then draw 1 card."

Indeed running Gemini Imps has served merit before, as a means of disrupting much feared XX-Saber Gottoms and Royal Tribute plays. With the coming of Dark Worlds, Gravekeeper players will be need to be especially careful as running Royal Tribute will become more of a liability than an asset and will need to be sided out according. However, Gravekeepers already have their own means of suppressing the numerous discard-triggering effects inherent in Dark World decks:  

Gravekeeper's Watcher

(Spellcaster-Type/DARK/Level 4/ATK 1000/DEF 1000)

"When your opponent activates an effect whereby your opponent discards a card(s) from his/her hand, you can send this card from your hand to the Graveyard to negate the activation of the effect and destroy it."

While it may not be capable of turning your opponent's Card Destruction into a -1 like Gemini Imps can, in a Gravekeeper Deck, Watcher has added searchablility, and that can be all too crucial in gaining control of the game earlier. Whether as a Gravekeeper player you'd rather retain card advantage or be ready to counter your opponent's strategy faster, ultimate that's a matter of personal preference.

Just be wary, the Blackest Night is coming.

Remember players, the game ends with you.

P.S: Different Dimension Ground is another solution to the Dark World threat, and it works against Fableds too. ^_^ Just another option to consider if you find the DWs to be that much of a threat. Shutting down potential T.G. plays isn't a bad idea either especially when they've surged in popularity of late.