In Rise of Berk, dragons can come in multiple rarities. The rarity dictates how common/hard to get the dragon is and provides a good measure of their power and abilities. The different rarities are:

• Common: These dragons can be obtained through Toothless Explorations and Journeys. You can own more than one of these Dragons. They are available year round.
• Uncommon: These dragons can be obtained through Toothless Explorations and from Ascension Portals. You can own more than one of these Dragons. They are available year round.
• Rare: These dragons can be obtained through Toothless Explorations, Journeys, Ascension Portals, and Card Packs. Some of these dragons can be obtained by completing Collections. You can own more than one of these Dragons. They are available year round.
• Elusive: These dragons are harder to get, and can only be obtained through Card Packs or by buying them from the Book of Dragons for Runes. Very few can be found in Journeys, Toothless Explorations, and Collections. You can own more than one of these Dragons. Some dragons are available year round, while others are Seasonal Exclusives and can only be obtained during their respective season.
• Unique: These dragons can only be obtainted through Card Packs or by buying them from the Book of Dragons for Runes. You can only own one of each of these Dragons. Some dragons are available year round, while others are Seasonal Exclusives and can only be obtained during their respective season.
• Premium: These dragons can only be obtainted through Card Packs or by buying them from the Book of Dragons for Runes. Some dragons are available year round, while others are Seasonal Exclusives and can only be obtained during their respective season. You can own more than one of these Dragons. They have some visual effects in the game that the other Dragons don't have (e.g. breathing fire/ ice or other unique effects when clicked on after reaching Titan level).
• Epic: These dragons can only be obtainted through Card Packs. Most are Seasonal Exclusives and can only be obtained during their respective season. You can only own one of each of these Dragons. They have some visual effects in the game that the other Dragons don't have (e.g. breathing fire/ ice or other unique effects when clicked on after reaching Titan level).
• Legendary: The largest and most unique dragons in the game. They can only be obtained by completing Collections, with some exceptions like Shellfire, or purchasing their respective Card Pack via in-app purchase. These dragons have their own roosts across Berk and boost different actions in the game. You can own only one of each. These Dragons cannot be moved, released or stored in the hangar.