What does that old key unlock?

Copied from pxfuel; used under Creative Commons License

1. The heart of another. The bearer of the key can cast up to three levels of enchantment spells per day.
2. The door to whose house? The bearer of the key can use any door as a teleportation device to a well-known place, once per day.
3. The clasp on a thick, brass-bound book that is actually hollow and can be used as a strongbox.
4. Nothing. Rather, the key can be used to magically lock any portal for one hour.
5. The mind of another. When pressed to the back of someone’s neck, the user can read their thoughts.
6. A large padlock that, if touched with any other implement. cries out, “Thieves! Robbers! To Arms!” for a whole minute.
7. The secret door in the cellar of a wizard’s tower.
8. The beast inside. The bearer of the key can transform into a ferocious animal for one hour.
9. The other beast inside. The bearer can turn into a chimpanzee for one hour. (This is a monkey.)
10. A city. The bearer of the key is usually treated in a friendly fashion by the citizens as long as they are in the city.
11. The magical manacles holding the great wyrm known as Render prisoner in its cavern.
12. The ties that bind. The bearer of the key is unlikely to be held or restrained.
13. Nothing. Rather, the key can be used to cast an imprisonment spell on one being it touches.
14. The secret of magic. The bearer of the key can learn and use up to three levels of spells per day.
15. The secrets of the universe. The bearer of the key can cast augury once per day, but has a 10% chance of contacting a great old one with the spell and going insane.
16. The gate to the Garden of Creation.
17. The secret of eternal life. The bearer of the key can heal their wounds and regenerate lost limbs, but slowly turns into an undead shadow of themself.
18. The secret to keeping a clean house. The bearer of the key can lock the door to a house when they leave, and it instantly becomes clean and tidy inside, but the magic only lasts as long as the door remains locked.
19. The vault of the Blue Temple, wherein piles of gold and jewels are stored. Agents of the temple know the key is missing and are actively hunting for it.
20. Cheat codes. The bearer of the key has the ability to cast wish spells.