To complete it, you must collect every single card of each type; a total of 120 cards, from the 199 available cards. The other 79 cards are duplicates (for example, there are three “Ghoul” cards you can find, but you only need one for this quest objective). 
- Northern Realms Gwent deck (40 cards)
- Nilfgaardian Empire Gwent deck (41 cards)
- Monsters Gwent deck (44 cards)
- Scoia'tael Gwent deck (41 cards)
- Neutral Gwent cards (29 cards)
Gwent cards may be obtained by purchasing them from merchants, winning against merchants at Gwent, and by winning against named NPCs in Gwent side quests. After winning against a certain number of generic merchants, playing against merchants will no longer earn new cards. The book A Miraculous Guide to Gwent (added by patch 1.20) can be used to keep track of the number of cards still necessary to obtain, and of Gwent side quests.
Journal entry Edit
- In his previous adventures, Geralt had gained fame as a master dice poker player. Yet having mastered all challengers in this arena, he had no choice but to find another in which to garner more laurels. He thus decided to take up gwent, and since he aimed to play at the highest levels, he felt he had to gather a complete collection of all the cards available – including some which could only be had by winning them off the best players around.
- Complete your collection of Gwent cards.
- This quest will fail if you do not win all the cards from the Gwent tournament at the Vegelbud estate during A Matter of Life and Death. Losing a match, or ignoring the tournament altogether would both result in the quest's failure.
- This quest will fail if you take the gold reward at the end of A Dangerous Game.
- This quest will fail if you lose the Gwent tournament at the Passiflora during High Stakes.
- This quest does not require the collection of Gwent cards added by the expansion packs.
- The book A Miraculous Guide to Gwent does not include the cards which came with the expansion packs.
- There are 2 easily missable cards in Velen. To get them you must free the Claywich merchant who is held captive to the east of the Claywich. Be careful, this merchant is bugged. Make a save just before opening his cage. Then make a fast travel to the Claywich. If talking option doesn't show up reload until it does. (Done with Patch 1.22) You can also play with him for a randomly earned card.