When connected to the PlayStation Network, online play is integrated into the single-player experience. Throughout levels, players can briefly see the actions of other players as ghosts in the same area that may show hidden passages or switches. When a player dies, a bloodstain can be left in other players' game world that when activated can show a ghost playing out their final moments, indicating how that person died and potentially helping the player avoid the same fate in advance. Players can also leave messages on the floor that can also help others such as forewarning safe or hostile positions, trap locations and tactics against enemies or bosses, among general comments. When playing with other players, co-operative play allows up to three characters to team up in the host's game world where visiting players appear in soul form that can only be returned to their bodies when a boss is defeated. In competitive play, players can invade a player's adventure as a Black Phantom to engage in combat with the host player. If the Black Phantom kills the host, they can be returned to their body in their own game whereas if killed themselves, the host gains a portion of the Black Phantom's souls.

via en.wikipedia.org

Why do I blog this? An interesting example of geolocalized communication pointed to me by my friend Mirweis Sangin. The idea here is that location-based written traces (left by other players) can inform and help.