Algalon, the first and true WoTLK progressive realm.
Every scene from the video has been recorded in Dalaran-WoW.
A brief explanation of the story:
Once upon a time in a world called Azeroth, there was a mighty enemy known as The Lich King, he was a huge threat to that world and all their habitants fought against him to free their lands from the plague.
When Arthas, The Lich King was defeated, one Titan had a nightmare with a vision of the future where one of the Dragons started a Devastation. He quickly convened a council with the rest of the Makers and decided to stop the time and send their Observer: Algalon with one specific task: "Be sure that everyone that steps into this world defeats every known enemy." With that, they will observe through Algalon's eyes where there is a solution to avoid this future that might come to us and save our world.
Now, the brave ones that dare to start again will help the Titans to find that little clue that can change everything, but in the meanwhile everyone is forced to progress through all the enemies, step by step, to be sure that they don't miss any detail.
This is the story of the WoTLK progressive realm Algalon from the private server Dalaran-WoW, we made a metaphor where the Titans are each one of the Staff members and where they create the realm Algalon to provide that progression to all the players that want to experience once again how it was back in days of Retail.
Correction on the credits: It is not "Curiosity" but "Kuriosity".