Spy Combo wants to ramp into Balustrade Spy and Dread Return reanimation or go wide with mana dorks and defenders, so the extra Arms of Hadar can pick off their small creatures like Elves of Deep Shadow, Quirion Ranger, Gatecreeper Vine, and Mesmeric Fiend. Its -2/-2 won't kill the bigger defenders like Wall of Roots (0/5) and Overgrown Battlement (0/4), so don't count on it to sweep the whole board. Okiba-Gang Shinobi punishes their grindy, card-advantage-heavy game plan by stripping two cards on connection, which can be devastating against a deck relying on assembling pieces. Agony Warp is awkward since many of their creatures (Wall of Roots, Overgrown Battlement) have high toughness relative to the -0/-3 half, and Mukotai Ambusher is replaceable. Keep Snuff Out and Cast Down for their relevant creatures, but remember Snuff Out can only hit nonblack creatures, so it can't target Balustrade Spy, Lotleth Giant, or Troll of Khazad-dum, while Cast Down can hit any of them as long as they aren't legendary. Removal can't stop an enter-the-battlefield trigger like the Spy's mill, so hold up Counterspell to stop Balustrade Spy and Dread Return before they resolve. Spellstutter Sprite can only counter a spell with mana value equal to or less than the number of Faeries you control, so it can't stop either of those (both have mana value 4) without four Faeries; use it instead on cheap plays like Elves of Deep Shadow or Lotus Petal, or on Land Grant and Winding Way once you have a second Faerie.