Cards have 1 of 5 rarity types. Cards with higher rarity are harder to find in Card Packs and are significantly more powerful. Rarity is indicated by the color of the set icon on the bottom of the card.
Legendary cards are special cards that are extremely powerful but also play a significant part in the lore. They are marked "Legendary" in the card type box. They are often characters who recur throughout the sets or play a significant role in that set's theme. A deck may only contain a single copy of each Legendary card, even if it is a reprint from a different set.