To upgrade a card, you need:
- Enough duplicate copies of that card.
- Enough coins to pay for the upgrade.
Each card has a list of upgrades it advances along as you upgrade it - called its ‘upgrade path’. The upgrade path shows the stats which will be improved by the next upgrade this card gets and the green, pulsing numbers show the current / new numbers for that stat.
The cost to upgrade cards will increase with each upgrade. Rarer cards need more duplicates / coins to be upgraded but have shorter ‘upgrade paths’.
Traits are special actions which the card makes the moment you deploy it to the battlefield. Each card has a single trait.
Traits are unlocked after you upgrade a card for the first time and can also be improved twice by further upgrades. The cards effect becomes more powerful as the trait is upgraded.