The Soul Sceptre is a one-use relic. Using it binds a permanent bonus to your current class. Changing the bonus requires a Retraining Tome, which unbinds the sceptre together with the class reset.
Mage picks one of two branches: Misty Veil (invisibility and speed for 3 seconds after every active spell) or True Power (spell-school amp and 0.3 health per Intelligence).
Craft: Soul Tormentor, End Crystal, Nether Star, blocks of redstone and diamond. Per-class bonus text is on each class page.