The Assassins' Creed: Revelations online pass grants access to online multiplayer and an exclusive character.
Activate your Uplay Passport code, which comes with new copies of the game, and you gain access to multiplayer mode and The Sentinel.
The multiplayer modes Uplay Passport unlocks include Wanted Mode, Artifact Assault Mode, Manhunt, Deathmatch, Corruption, Steal The Artifact, Assassinate, Chest Capture and Training Ground.
The Sentinel, Vali cel Tradat, is described as a Wallachian noble by birth and a former Assassin.
As with other online pass schemes, if you don't have a code you'll need to pay to access the content. With Uplay you can buy a new Passport code online or activate a free trial.