Black Iron Mill

I've been tooling around with this deck since Beta and Defiance finally gave it the tools to be competitive.

Before Defiance, you really relied on the combo of Black Iron Manacles and Solitude for the kill; but sometimes Solitude wouldn't be a large enough hit to finish the job. But Mournful Deathcap changes things. It fills your opponents bin ahead of time so Solitude is almost always lethal with a manacles and you can even just deck your opponent with Solitude if they leave your Deathcap alone long enough.

Deathcap of course also pairs amazingly well with Dreamsnatcher. I think the best opening hand is: Turn 1 Crest or leave up Torch, Turn 2 Dreamsnatcher, Turn 3 Deathcap + Power card. It is entirely possible to win a game with just Dreamsnatcher beatdown.
Shakedown Also helps the Dreamsnatcher of course as well as with the Manacles.
The Dreamsnatcher and Deathcap have really helped the deck avoid getting run over by aggro decks.

The Ixtun Merchants are there because the Manacles can really hamper control decks and reanimation decks, so you want to make sure you've got that online as much as possible. And of course Bore can be an absolute savior.

Naturally the removal suite changes with the metagame. Devouring Shadow usually gets -3 to -5 by the time you've got something worth casting it on. In Cold Blood synergizes with Dreamsnatcher and Manacles against Justice cards.
I've cut back on Devastating Setback since adding Ponysnatchers; sometimes its a 4 for 1 and sometimes its an overpriced Sabotage. I've swaped it for a Stray into Shadows in the Market since Stray doesn't cripple opposing boards as much right now.

The Treacherys could come out though I'm generally happy with them and they help with the drip damage that the Manacles do.