Oops, All Spells is a pure combo deck that mills its library with Balustrade Spy or Undercity Informer, then reanimates Thassa's Oracle or Dread Returns back key pieces for a same-turn win — it can go off as early as turn one with enough free mana. Leyline of the Void is your primary hate piece: if it's in your opening hand it enters in play before the game begins, shutting off their entire graveyard-based combo and leaving them with no path to victory. Your own engine is unaffected since you reanimate into play directly rather than from the graveyard once Leyline is out. The discard suite (Thoughtseize, Unmask, Cabal Therapy) is critical for disrupting their fast hands when you don't have Leyline, so keep it intact. Trim a Cabal Therapy and the less-impactful reanimation targets (Archon, Ashen Rider, one Raph & Mikey) since this race is decided before battlefield presence matters — speed and disruption win this matchup.