The first time I ever blew past 200 in Gwent my self monologue changed to 'I am a feckin' god of gwent!!!'
But really, once you get your commanders horns, spies, stacking units (Blue stripes, dragon hunters, CATAPULTS!) and the odd decoy or scorch card, you're pretty set. Northern realms seems the one to most reliably get high values in each game. You might be able to do higher overall with monsters, but I'd imagine it'd require pretty much emptying your deck.


