Medusa Sheild is killing blind and undead, bug?

[Ewierl]

Argitoth said:Ghosts have no substance to turn to stone.

They have substance, it's just ethereal. "Ethereal" is not "nonexistent." Remember, you can chop up a ghost with swords, it's just harder to do so. Petrification is a magical event, not a physical event.

There is a different tag out there that denotes "really really has no substance"; it is the "Truly Etheral" trait possessed by some Doom Horrors. It provides 75% protection against non-astral magic... presumably this would block Medusa petrification in the same way as it does the spell.