In Splinterlands, cards are only leveled up by combining like cards. Here is a quick guide on combining and leveling cards.
BCX
BCX = Base Card Experience - Every single regular card that is found in either a Loot Chest or a Booster Pack is 1 BCX, meaning that it has not been combined.
A player can combine 2 versions of the same card to create one card with a higher BCX. Once two cards are combined one card will be burned and its BCX will be merged into the Card ID of the card holding the highest BCX before the merge. In the case of both cards having the same BCX prior to the merge, the Card ID of the first card selected will be held.
Example 1:
Card 1 = 1BCX
Card 2 = 1 BCX
In this example, if a player chooses to combine Card 1 and Card 2, Card 2 will be burned and its BCX will be merged with Card 1. The player will now own Card 1 with 2 BCX
Example 2:
Card 1 = 1BCX
Card 2 = 2BCX
In this example, if a player chooses to combine Card 1 and Card 2, Card 1 (Holding the Lowest BCX prior to the merge) will be burned and its BCX will be merged with Card 2(Holding the Highest BCX prior to the merge). The player will now own Card 2 with 3 BCX
Once a certain card has reached the required BCX, it gains the corresponding level.
Leveling Up
On the STATSpage of each card, you can see how many BCX of that card are required to reach each of its different levels, and what stats and abilities correspond to each of those levels.
This Common Alpha Edition card requires 379 combined singles to reach the max level of 10.
This Untamed Legendary requires 11 combined singles to reach its max level of 4.
The number of BCX required to level up cards varies depending on the Card Set Edition. Alpha cards require the fewest to level up because there were far fewer Alpha Cards in the original supply.
Combining cards is permanent, and there is no in-game benefit to combining until the next level has been reached.
In the above example of Phantom of the Abyss, once 6 have been combined the card reaches level 3. If 4 more are added, bringing that card to 10 BCX, the card will still only be playable at level 3 until 1 more BCX is combined into it.
Cards that are combined are deducted from thecirculating supply.If 20 single cards are combined into a 20 BCX card, the circulation of that card will be reduced by 19.
Because they are significantly rarer, Gold Foil Cards require fewer BCX to level up than regular foil.
This Gold Foil Untamed Legendary requires 4 combined singles to reach its max level of 4.
Where the regular foil Phantom of the Abyss requires 11 cards to reach its max level, the gold foil edition of the same card requires only 4 cards.