The Artifact (Iris)
From Halopedia, the Halo wiki
The fifth episode began with people putting together star images from all the servers, revealing the phrase "The Artifact Location". This lead people to a website that directed people to locations in New York, Seattle, and Los Angeles. At those locations the final server link was revealed. The fifth server detailed the mystery of Earth and how Humans may answer the Forerunners own mysteries, and revealed the identity of the mysterious entity who hijacked Adjutant Reflex as "MB05032" and that they will be waiting on the Ark.
Server 5 opened on August 16 at Halo3.com. The background has changed for this particular server, however, the Forerunner object seems to be the same.