Champions is one of the unit cards that a player can own in the game Legends of Runeterra. However, unlike Followers, they are much more powerful and have complex mechanics. Because of that, decks often build around champions.
A player can own duplicates of a champion, however, when the champion is active, their duplicate cards will transform into special spells, similar to the ones existing, with a unique addition action: Shuffle a copy of the champion card into the player deck.
For example: Player is owning 3 Ezreal cards. When an Ezreal is played, the other 2 cards will transform into Ezreal's Mystic Shot. In addition to the normal Mystic Shot effect, Ezreal's Mystic Shot shuffles an Ezreal card into the player deck.
Champions can level up, by fulfilling their level up requirements. Level up usually gives the champion card better stats and better abilities. Once level up, future cards of that champion, played in the same game, is also level up.
In normal game mode, a player can have at most 6 champions in their decks. These cards can be from different champions, or have duplicates. Just like other cards, a player can have at most 3 duplicates of one champion.
In Expedition, a player has 2 champions in their initial deck. As the player progress in a trial, they can earn more champions cards.