don't know about Demonic Mask but Painskull is pain in the ass for 50 battles after which it turns into Dead Skull(?) which give +5atk +5 int
Silver Rapier is weapon you can obtain by finding recipe (don't know if it's random), you can give it to guy in Magic Guild and he can make Silver Rapier for you but the cost is massive - 5 Mind Runes!! 2 Magic Crystals and some money.