Allows the player to be summoned by other players to their world as a Blue Phantom for co-operative play. A blue sign then will appear in their world which displays the player's name, total number of multiplayer sessions and co-op evaluation score. In order to use the eye stone, the player must be online, in Soul form and within the allowed area of the level (usually at its beginning). If the players defeat the boss, the summoned players will be sent back to their world, and will recover their body.
Players can only see blue summon signs if their owners are within 10 levels (+/- an additional 10% of their current character level). For example, a level 100 player can choose to summon anyone between level 80 and level 120, and a level 30 player can choose to summon anyone between levels 17-43.