From Dragon Mania Legends Wiki
Main Island (next to the Lighthouse and Totem of Friendship), the Clan Fortress allows Trainers to join or create Clans. It was introduced along with the release of the game, but was only activated in Update 2.0
The Clan Fortress was destroyed when the Enigma Egg crash-landed on it. The Fortress can begin to be rebuilt and leveled by creating or joining a Clan. As the Clan reaches certain levels, the Fortress will change its appearance.