That does only work with auras you have already learned. Your health will be reset to 100, your armor to 0 and your mana to 100. You will also respawn somewhere in the level. Well, but you keep your spells and books. So think about it once more.
Magical rings are rare to find.
If you found one you must identify it to use its powers. You can only have one ring at a time. After identifying your ring you will get to know the ring's name. The name shows the attributes of your ring. A ring can regenerate you, damage you, have additional power, and so on.