Some more art from Brian "Glad" Thomas...
Chance of Addiction: 75% per use
Cost: 300 gp
These colorful leeches subsist on ocular fluids, injecting a powerful narcotic as they consume the user’s sight. A leech will feed for 1d4 days. The leeches, for some reason, will only feed in pairs, with one on each eye. One-eyed men are thus unable to experience the ecstasies of eye-leeches.
Visions of the future, that May or May Not come to pass
Leech-Sight - while the leech feeds, the user has 30’ of vision into the ethereal plane
Blindness - it’s hard to see through a leech sucking out your eye juice
Eye Humor Loss - 1 hit point per day is lost to the leeches
Addiction: Addiction is caused simply by permanent blindness, as the leeches suck out the last of the ocular humors. Once this occurs, the user is compelled to acquire more eye-leeches to make use of their leech-sight.
Withdrawal: Withdrawal is likewise simple - if a blinded eye-leech addict is unable to acquire the leeches, he cannot see.