Stone Skin Potions can drop from the Master Alchemist. Drinking one increases defense by 19 points, turns the user's skin gray, and slows them down. To guarantee successful consumption, a drinking level of 15 is required.
Lysis buys potions of stone skin for 60 gold and sells them for 250 gold. Darklow buys them for 48 gold and sells them for 280 gold.