Avran's Curse is the set of negative effects the Sealing had on the demons. For one thing, it tied them even more closely to their home in the Obsidian Mountains. If they leave it, it drastically weakens them physically and magically. The other main problem created by the curse is that if demons come into contact with water, the touched area turns temporarily into obsidian. They can still control any obsidian body parts, but they are much more cumbersome to move, and hurt tremendously. Most demons prefer to avoid this state at all costs. It does, however, have its advantages- an obsidian limb is much harder and heavier than a normal one. The Obsidian Lord, in particular, has used this ability to its fullest.