Mono-Black has almost no artifacts or enchantments, so Annul is largely dead; trim it along with some Prohibit copies since their key threats (Hypnotic Specter, Nantuko Shade) often cost 2-3 mana but Swords to Plowshares answers them more reliably. Exalted Angel is a great flying body that gains life against their aggressive Dark Ritual starts. Be careful when morphing it, though: face-down it is a 2/2 with mana value 0, so Smother can still kill it, and only the face-up Angel (mana value 6) is outside Smother's range. Arcane Laboratory slows their disruptive one-two punch of Duress/Cabal Therapy plus a threat in the same turn. Keep Wrath of God as your sweeper and all Swords to Plowshares as your best spot answers against Hypnotic Specter and Nantuko Shade.