User blog comment:ЭЛЯ (не могу войти в аккаунт)/I've seen such a dragon .../@comment-24568135-20140813172258

Anniversary_Islandwas available to anyone on the iOS so they aren't rare in that way. They can't be bred and you could only get each one for a 24 hour period so in that way I guess you could say that they are rare.