Once per turn: You can target 1 monster in your opponent's Graveyard; discard 1 Fiend-Type monster and banish that target.
Dark Smog is amazing in Darkworlds. It is a perfect outlet to Discard their Darkworld Monsters so you not only get to Banish a card but you get the effect of the Darkworld you discarded too. Being able to control your opponent’s Graveyard while setting up your own Graveyard is just want Darkworld’s needed since you won’t always have a Dark World Dealings to start setting up your grave and getting your Grapha, Dragon Lord Of The Darkworld is something you need to do as soon as possible. What is also nice is that in most cases your opponent will have used up their Spell and Trap removal on your The Gates Of The Dark World meaning that they won’t have anything left to destroy Dark Smog.
In Darkworlds this turns every Monster in your hand into a D.D. Crow that nets you advantage. This card is the perfect mix of tech and combo and will see play in Darkworlds so long as the Graveyard is important, so forever.