Gro-a-tog runs a healthy density of black cards — Psychatog, Duress, Smother, Sickening Dreams — so Compost triggers regularly as those cards hit their graveyard, generating steady card advantage over a long counterspell war. Hydroblast has no red targets here and stays boarded. Xantid Swarm, free through Aluren, lets us attack to turn off a Counterspell or Foil right when we need to resolve our engine pieces. Cut Bone Shredder and Mesmeric Fiend since Psychatog is their only real threat and dies to Man-o'-War's bounce or gets outgrinded by our card advantage, two Wall of Roots since the matchup is about resolving spells through countermagic rather than ramping, and Sylvan Library since we don't want to pay extra life into a deck holding Counterspell and removal.