Eye Stones - Demon\'s Souls
Here are the differences between the eye stones-
Blue Eye Stone- Can only be used soul form; used to leave a soul sign, which when picked by a living person, can summon you to aid them to kill a major demon. In return for killing the demon, you get your soul back and the summoner gets the demon's soul and the seperate souls as a bonus for killing the demon, you, unfortunately you don't get the souls.
Red Eye Stone- Used for people to duel other people, can be used in soul or living form. Can be used as a scoring too, you can be judged over your dueling performance, the one who loses the duel is penalized...
White Eye Stone- Used to banish Black Phantom from your server after which they cannot come back; can only be used in living form considering that black phantoms come using black eye stones in soul form and can ONLY appear in living servers.
Black Eye Stone- Can only be used in soul form; used to turn you into a black phantom, you go to other servers of live people. If you kill them, you regain your soul, if you die, you are banished from that server but you don't have any extra penalty for dying as a black phantom, but if you kill them they die, turn into soul form, and lose all their souls.
Please do not be rude to others, what may be obvious to you may not be to the person asking the question.