I've had immense success with this deck. It's very flexible, allowing you to adapt to what the opponent throws at you while still allowing you to completely overwhelm and overpower them in the mid-to-late game. This deck rewards you for having a big graveyard, and because milling decks are so popular now (looking at you, mono-blue), the best way to drive your opponent mad is to have an effective self-milling deck.
Most cards are midrange, so ramping up lands is essential in this deck. Migratory Greathorn and Growth Spiral provide quick ways to do just that. In a pinch, you can sacrifice life for any the multicolored lands aside from Zagoth Triome. Mid-game, Molderhulk continues to allow you to amass lands. You can still get a few creatures onto the battlefield early, such as Fiend Artisan, Merfolk Secretkeeper, Chainweb Aracnir, and Barrier of Bones. Wilt is cheap and allows you to counteract early setup of opponents' enchantment-heavy decks (looking at you, mono-blue). Mid-to-late game, you can use Scholar of the Ages to bring back Wilt to further decimate the opponent's battlefield. Meteor Golem also works well for this purpose. Midgame, Frilled Mystic acts as an effective counter, costing only more than Cancel while adding a creature to the battlefield on your opponent's turn. As this is a creature spell, you can cast this card from the graveyard with Back for More during the opponent's turn, though admittedly this is the more expensive option.
Fiend Artisan has two benefits: it can become immensely powerful after enough milling, and it can be used to summon the big guns as a last resort if they're not yet in your graveyard.
To keep your life from running out, Molderhulk or Gyruda, Doom of Depths can be summoned from the graveyard with Unbreakable Bond, giving them lifelink as well as a lower casting cost. Mid-to-late game, you'll probably want to use Unbreakable Bond on a Fiend Artisan, provided your graveyard is big enough to make it worthwhile.
Yarok, the Desecrated is the star of the show here, since it allows you to be twice as effective when summoning creatures, most of which have abilities that are triggered when entering the battlefield. When Yarok is in play, Meteor Golem can take out two permanents, crippling the opponent. You might even manage a third if summoned with Back for More. Likewise, you can get two lands with Molderhulk, or deal 4 damage twice when summoning Chainweb Aracnir with its escape cost.
As an added bonus, if Scholar of the Ages dies, you can get her back into the battlefield with Back for More or Unbreakable Bond. This will put the spell you just cast back into your hand, plus another instant or sorcery, so it's a free transaction. Sacrifice her with Crypt Lurker or Fiend Artisan to keep the loop going.
Note that the mana curve looks wonky, but that's because Migratory Greathorn's CMC is on its own. However, the ideal situation is to mutate it onto something, which is cheaper, at .
