After reaching legend with Cubelock, I started experimenting with fun handlock decks. To my amazement, this deck turned out to be a monster in Diamond 5 MMR.
When compared to cubelock, this deck always has a play on turn 4, with Twilight Drake, Mountain Giant and Voidcaller. Being able to Life Tap for only 1 mana is massive, as it allows you to tap and play Doomsayer or Kanrethad Ebonlocke on turn 3 followed up by a big turn 4.
The deck plays much more aggressively than cubelock. You can often play massive minions one after another starting turn 4. Basically play the most threatening minion each turn and pressure face as much as possible. At some point you have too much pressure and the opponent runs out of removal. I have literally been able to set up lethal 5 turns in a row against a rogue after having my board cleared with multiple Zephrys the Great.
Against aggro this deck is weaker than cubelock, mainly due to missing Voidlord and Mal'Ganis. However cheating out Fel Lord Betrug has won me multiple games against secret mage. The removal in this deck is less consistent, but in return it offers more healing from Aranasi Broodmother and Plot Twist, as well as Nether Breath (though not consistently).
Fel Lord Betrug hasn't been a great card in Standard, but thanks to Voidcaller, Emperor Thaurissan and 1 mana Life Tap it is a legitimate inclusion. Having a very minion heavy deck basically makes him a board clear like Twisting Nether with an upside of possibly generating demon and deathrattle value. I think he really deserves a spot in this deck. EDIT: I am testing a version without that replaces the Betrug package with Expired Merchant, Hellfire and Dragonmaw Sky Stalker.
Keli'dan the Breaker is in my opinion better than Siphon Soul in most situations. You can in theory get a Twisting Nether effect if you draw him with Plot Twist, although this hasn't happened to me once after more than 40 matches. EDIT: Keli has been very useful for enabling lethals through taunt and pushing face damage, but I think Maiev Shadowsong does the job way better. I don't have the card, nor am I crafting it just to test it, figure out which one you prefer or have in your collection.
Try the deck if you have enjoyed Handlock in the past, this is definitely my favorite iteration ever.