Regarding the "Rosetta Stone"... let's *not* make it a stone, they'd be expecting that

. There's no reason we couldn't have multiple aids for reading the inscriptions. For example, I would make the +2 bonus in #15 a non-stackable insight bonus (seems to fit better). Then we could also have a translating dictionary between hieratic and hieroglypics in the library, giving a circumstance bonus (for being able to consult the dictionary) that reduces the hieroglyphic DC to the hieratic DC +5. And perhaps a set of notes by one of the gnoll clerics that gives another +2 circumstance bonus to both DC's. Combining all three, hieratic DC would drop to 16, and hieroglyphic to 21 (or 19, depending on how the last two stack).