Mono-Black Midrange attacks you on two axes: hand disruption via Duress, Cabal Therapy, and Ravenous Rats, and a steady stream of efficient threats like Hypnotic Specter and Nantuko Shade. Ravenous Baloth provides a resilient threat that laughs at Smother and Snuff Out, giving you a must-answer body that also gains life against their attrition plan. Pyroclasm and Simoon help deal with Ravenous Rats tokens and, post-board, the Phyrexian Negators they may bring in — be cautious with Pyroclasm if you have Grim Lavamancers or Mogg Fanatics you need. The Naturalizes come out because they have very few relevant artifacts or enchantments main, and Rancor and Seal of Fire are your weakest cards against a deck full of removal and 2/2s; your burn suite and Quirion Dryad do the heavy lifting here.