I'm not sure what denotes it, but I think it might be hero cards. If you do the Gwent quests, you will naturally get high quality cards. I only played the mission card battles and was able to enter the tourney.
I finished all the Gwent quests yesterday. I didn't touch the card game for a long time, but it is easier to understand than I first thought. Decks only being around 25 cards is a godsend. I can't manage this 60 card stuff. Battles are also pretty quick so even if you lose it doesn't feel like you wasted a lot of time. The four sets are very diverse and allow for different types of decks in each style. I would like to see a standalone version for sure, but I think it would need some rules changes. You can basically stack your deck with hero cards. While there are some disadvantages to doing this (like no commander's horn), it generally is a fast track to victory. Of course there is strategy involved, but most victories seem to stem from solely having the best cards. Some cards are clearly better than others. Why have two of the Blue Stripes Commandos with 4 attack power and the buddy up ability when you could have two Crinfrid Reavers with 5 attack power and the same ability? Maybe if the game had a limit on how many hero cards you could put in, it would be a bit more balanced.
Also I don't like the fact that there are missable cards. It kind of punishes people who aren't completely devoted to this game right out the gate.
