Board Thread:Questions and Answers/@comment-73.131.186.173-20151227013812/@comment-1738746-20151227022821

Because when a dragon is first released, the rarity gets set as "Uncommon" while we wait for the ratios to settle and see what the true rarity is. Once we knew it was rare, we just forgot to update it on that particular page :P It's changed now- the dragon's article will always show the correct rarity, so if you see something else written on a different page, you're welcome to change it so it matches the dragon's article!