A new map is on the way for the multiplayer modes in Assassin's Creed: Brotherhood once the game's community reaches a set number of online kills.
An announcement on Ubisoft Germany's official AC: Brotherhood website (via Joystiq) revealed the multiplayer event, which will unlock the "Rome by Night" map as players top a cumulative 25 million kills.
The progress bar on Ubisoft's Assassin's Network community site lists the current total at zero kills, so it's not clear if the tracking isn't functioning properly or if the promotion simply hasn't started yet. Either way, now's as good a time as any to start working on your backstabbing skills.