There are three fun decks to make around this card, each one focusing on one of the colors. This one is almost mono-black. I tried a white weenie and a goblins shell and both were just not that good with Butcher of the Horde. This shell is the one that works out well in Modern.
This deck uses devotion to black as a minor effect, yet I was able to have enough devotion for Erebos to become a creature often enough.
Inquisition of Kozilek is very good in this deck. With the ability to draw it early and the two other major threats (Path to Exile and Lightning Bolt), it is fairly common for this deck to disarm an opponent in the first three turns.
Here my first Erebos takes negative counters from a Wither creature and I am able to play a second one.
In this deck Meddling Mage made Blood Artists dead in my hand for the early game. But once I played Geralf's Messenger it was GG.
Here is a case of me using the three disarmament spells to trim my opponent's hand of threats.
Here I faced a deck with a ton of target removal. I was able to attack around all that target removal and the occasional hand discard.
Whip of Erebos won me this game. Even if I sacrifice the creature, I can bring it back for a swing.
Look at how much removal and discard my opponent was packing.
But at some point my opponent ran out of cards and I could swing for the win.