From Halopedia, the Halo wiki
Ennobled is a Bungie.net campaign medal available in Halo: Reach. It is earned by completing a campaign mission with four players on Legendary difficulty. It is represented by the Noble Team emblem on top of a gray hexagon. The medal does not appear in-game and can only be viewed on Bungie.net.
On March 31, 2012 Bungie.net ceased updating Halo game stats and player records, transferring all record-keeping responsibilities to Halo Waypoint. As Ennobled could only be viewed on the site, it is effectively no longer awarded.