Can you put ranks into a knowledge skill on a specific subject?

[harmor]

Like could I have:

Knowledge (Areshkagal)
or
Knowledge (Absolom)

etc. If you can, how would the DCs be adjusted?

[Hawktitan]

DM fiat

[blackbloodtroll]

Ranks in Knowledge(Local) should suffice.

Perhaps, a book(masterwork tool) will be something to provide a circumstance bonus.

Discuss with your DM, as it is a flavorful, and not overpowered thing.