Card Leveling
Cards have multiple levels. At the start of a game, all of the cards in your deck are at level 1. When you play or directly discard a card, the next level of the card is put into your discard pile. At Rank Up
you reshuffle your deck, allowing you to draw your higher level cards.
A card at its highest level will not level further, but will still go into your discard retaining its current level.
Some cards have effects that allow you to level additional cards from your hand.