Derren said:
Except that this isn't something you can find out through a diplomacy check. That would require a knowledge local (or however this is called) check, some background research (I know, too much Shadowrun...) or at least a Insight check.
Also this information is very situational and most of the time this topic won't come up unless the PCs follow a script.
Were does it say that Derren?
Diplomacy is a skill you use to get something done. During your diplomatic overtures you discover something. This is why I called it an easter egg. You are taking the rules in a VERY narrow context and not using them for what they are supposed to be used for.
This skill challenge says that if a character interacts with the Duke in some diplomatic way they will learn something that will lead them to discover how to approach the duke about his past, and may even discover something about his past.
Example:
Player: I use my diplomacy on the Duke to tell him he can trust us. "insert random rp".
DM: I don't trust very easy and I am not sure about you. I can't put my finger on it but I will give you a chance.
Player: I roll history to see if the Duke has something in his past with people like us.
DM: You remember hearing a tale from the Dukes youth about someone who betrayed the Duke. That person was Eldarin like you, but from the southern provinces which we all know about the southern provinces.
Player: Surely you can not fault all Eldarin for the mistakes of a certain group of rabble we deal with. I can't tell you how many times I have heard about those southern country bumpkins leaving a path of deception in their wake. I am from Northern Eldarin from the town of Berkshire were we are renowned for our good nature.
Duke: Hmm perhaps your right, I should be a little more understanding I have a cousin who is the same way, and he is a prince *insert chuckle*
Insight in this case won't reveal that one tidbit because you wouldn't have thought the Duke would distrust you at face value until you engaged him in that manner. You could argue that other skills may have accomplished the same thing, but in reality its up the DM how he hooks in his easter eggs.