Gro-a-tog's threats and card selection are blue-heavy — Psychatog itself is a blue-black creature, so Pyroblast can destroy a resolved Psychatog outright or counter their Counterspell, Foil, or Gush to protect your own combo. Rushing River bounces a growing Psychatog back to hand, resetting its discard-fueled pump for the turn. Tormod's Crypt exiles their graveyard, denying Psychatog's ability to exile cards from it for +1/+1 and cutting off any Accumulated Knowledge value tied to graveyard count. Tsabo's Web and Crystal Vein come out since their manabase is mostly basics and Polluted Delta with little to punish, so you'd rather hold up direct answers to their namesake threat.