Rare books have been added to the loot tables that, with the right lore skills, can be deciphered and potentially reveal a clue to a true name. If you fail to decipher such a book, you can let someone else try who might have better lore/knowledge in the area. Make sure it is someone you trust though, or they could steal the knowledge in the book.
Finally, a true name can be a very valuable trade commodity. You are free to share a true name (or sell it) as you see fit. But remember, these beings are unique, two casters can't both call on the same one at the same time. So most casters would probably want to keep a true name secret.
- Diamond: lesser beings up to 15 HD
- Canary Diamond: beings up to 20 HD
- Blue Diamond: higher beings with no known limits
To call a being bound to a Planar Focus, use the appropriate calling spell and target the focus with it, and the being will be called.
- When inscribing the true name into the gem, a Lore: The Planes skill check may reveal some information on the being before you call it.
- If a being is killed, it will not be possible to call it again for 24 hours. This "cooldown" may be increased later, or other penalties considered. Don't let a called being die, that is not part of the agreement you made with it...
- These beings can be stronger, smarter, weaker, uglier, even completely different from those normally called by the calling spells. But they are all subject to QC/dev balance so don't expect to be calling demi gods (well you can always ask a DM to let you do it and see if you survive it)
- And probably a bunch of other things that I forget to mention right now.