Witcher 3 Gwent cards by faction
Every playable Gwent card in The Witcher 3, grouped by faction: Monsters, Nilfgaard, Northern Realms, Skellige, Scoia'tael and the neutral cards any deck can use. Each card lists its strength, the row it is played in, whether it is a hero or a spy, its ability and where it comes from.
Most Witcher 3 Gwent cards are bought rather than won, so the sources are worth reading before starting a collection. The merchants page lists which innkeepers and traders stock which cards.
Building a Gwent deck that works in The Witcher 3
A Witcher 3 Gwent deck needs 22 unit cards minimum, and only the strength printed on units counts toward a round. Heroes ignore weather and most effects, spies hand the opponent points in exchange for two cards, and medics pull a unit back out of the discard pile.
Cards sold by innkeepers are finite: each merchant carries their stock once, so buying out every tavern you pass is the reliable way to reach a competitive deck before the Gwent quests start.