Archfiend

Even six years after his TCG-release I'll try to build this deck around Archfiend Emperor, the First Lord of Horror and his (slightly?) better halve Archfiend Empress. But this time both of them will be supported by the recently released Curse Necrofear and the Dark Spirits from Legendary Duelists: Immortal Destiny. Foremost by the Dark Spirits - their effects allow us to special summon those heavy hitters Emperor and Empress from the grave during the damage step if your enemy attacks or if your enemy activates an effect, after you discarded them for twin twister for board clear or searching costs for the also new released Dark Spirit's Mastery spell. And don't worry about them effectless - you extend your board with the help from Archfiend Palabyrinth.

The Extra Deck choices are kind of optional, because Archfiend Emperor, the First Lord of Horror only allows other fiend-type Monsters in his entourage, but Monsters like Number 49: Fortune Tune and Wind-Up Zenmaines can help you stall for a while, if you bricked a little. And with their effects they can also get off Archfiend Heiress search effect. Except Coral Dragon, which is a good card, let's you draw and you can go for higher Synchro Monsters if you want, the others are Archfiend Cards, which can later be used for the effect of Archfiend Emperor, the First Lord of Horror and Archfiend's Roar (which is also a Archfiend Card for Emperor).

At the moment I have no clue what to put into the Side Deck, because in the current Meta Archfiends have not the slightest chance to compete.