Ooh, good books! Its been a long time though.
Rings of Power: Wonderful trinkets that can be sought out at Rivendell, Lothlorien, Barad Dur, and anywhere you see a Grey Wizard. They give the ability to be invisible, and can give increased power in building, combat, mining, or magic.
Warning: Side effects may include: Slow transformation into a wraith, obsessiveness towards ring, intensity of emotions, and having your mind taken over by a Dark Lord.
