Dawn of the Sixth Age

After the quest The Outcast, you had completed all of the quests and been to every place, unlocking all music tracks in the Fifth Age RuneScape. Once you talk to General Summer in Archosaur, you will be teleported back to RuneScape and appear in Varrock, but in a whole new age, the Sixth Age.

You can still return to the Fifth Age by talking to the Mystic in the Varrock Palace, but there will be no more quests for you to do in the Fifth Age zone. In this new age, you will be able to access many new skills and new quests as well. This is considered the age of exploration, where much more of the Western and Eastern Realms will become available to you.