Upon clicking any of your cards within your collection, you may notice a column defining a card's BCX, or "base card experience", located next to any cards' "Lvl" (level). BCX represents the total number of this copy of a card that were combined into the one card, which eventually affects a card's level once enough copies are combined.
Upon clicking on the "stats" tab within the same page displaying the BCX of the card, you will see a list of levels this card is able to achieve. Right of the levels you will see a column that displays the amount of cards needed to be combined to achieve the listed level for the card (circled in green). If you want to level this card up to level 4, then 25 copies are needed. If you want to level this card up to level 5, then a total of 40 copies are needed instead.
To the right of the "LVL" and "CARDS" columns, you will see four columns displaying the colors grey, blue, purple, and gold, which in order, these colors represent "common", "rare", "epic", and "legendary". For a summoner, like within the image above, this allows you to determine what levels your monsters will be capped to, while summoners' level caps are linked to a league instead.
The league caps can be found in the battle screen.
As you can see here for an example, the league limits in the silver league for summoners are as follows:
- Commons: Level 5
- Rares: Level 4
- Epics: Level 3
- Legendaries: Level 2
When entering a monster's stat page, you will see columns representing various attributes and abilities, which have slight differences per level. Sometimes a card may lose an attribute point during a level up, but in exchange the monster will get an useful ability. An example of this can be seen above in the card "Demented Shark" losing one point of max health in exchange for gaining the ability "Thorns" when advancing from level 5 to level 6. Sometimes they may even lose a lesser attribute in exchange for buffing a more powerful attribute as well, such as when the Demented Shark reached a total of 220 cards combined (level 8). At this level it loses the point of health again after having just gained it back the previous level, but gaining an extra point of melee attack power.
Circled in red above on each of these cards, you may see the rarity bubble for each card. The grey bubble on the Demented Shark represents the common rarity. The purple bubble on Lobstradamus represents the epic rarity. So in silver league, if you utilize a level 4 rare Kelya Frendul summoner as displayed before, you can use the Demented Shark up to a maximum of level 5. Lobstradamus can be used up to a maximum of level 3. If you only possess a level 1 Kelya all monsters will have stats downgraded to level 1.
When this happens you will see a message: "This Monsters's level is limited by the level of the currently selected Summoner. Level up your summoner to use higher level of this monster". This situation can be be recognized by the yellow triangle with the exclamation mark.