The Blue Eye Stone is a summoning item in Demon's Souls In-Game Description Proof you have been accepted by the monumental as a demon slayer. When you die and enter Soul form, use this to send a Soul Sign. This item can only be used in Soul form. A Soul Sign is sent to other worlds, and you are summoned from those other worlds as a Phantom. If you succeed in helping the summoner defeat a demon, you will regain your body.