Valgrim can pretty confidently say that there are no traps and no secret doors.
After some fiddling, Vug gets all the chests open.
Chest 1: 20 leather bags, each containing 1,000 gp.
Chest 2: A leather bag containing 1,000 pp, 9 leather bags each containing 2,000 gp in assorted gems.
Chest 3: Several racks containing potions and other magical elixirs. In all, this chest contains 10 potions of cure moderate wounds, 10 potions of undetectable alignment, 10 potions of nondetection, and 10 elixirs of truth.
Chest 4: A number of magic items: a ring, a rod, two wands, a belt, a cloak, a cloak, a harp, a silk pouch containing four small beads and a large leather-bond ledger with no title. It seems to be an out-of-date list of items in this treasury, but it also radiates magic.
Here are Bubba's Spellcraft checks:
Ring: 1d20 + 21 ⇒ (7) + 21 = 28
Rod: 1d20 + 21 ⇒ (15) + 21 = 36
Wand: 1d20 + 21 ⇒ (19) + 21 = 40
Wand: 1d20 + 21 ⇒ (14) + 21 = 35
Belt: 1d20 + 21 ⇒ (14) + 21 = 35
Cloak: 1d20 + 21 ⇒ (3) + 21 = 24
Cloak: 1d20 + 21 ⇒ (2) + 21 = 23
Harp: 1d20 + 21 ⇒ (16) + 21 = 37
Beads: 1d20 + 21 ⇒ (16) + 21 = 37
Ledger: 1d20 + 21 ⇒ (7) + 21 = 28
Let's see, we have: a ring of evasion, a rod of flame extinguishing, a wand of lightning bolt (23 charges, caster level 8th), a wand of haste (19 charges), a belt of dwarvenkind, a cloak of arachnida, a harp of charming, and four beads of force.
I accidentally wrote up the cloak twice.
The book is under the effect of Secret page, so it's hard to tell what it really says.
Hearing that the book is under the effect of Secret Page, Friar prays for guidance and strength and invoking his god's power, tries to dispel the magic hiding the contents of the book:
Dispel Magic check: 1d20 + 14 ⇒ (11) + 14 = 25 vs. DC of 11+CL of spell
Now you really hit the jackpot.
Friar's magic dispels the illusion and a totally different text emerges, in a different hand. The ledger is an exhaustive list of the members of the Ebon Triad, including its numerous allies and the locations in which these individuals live. You recognize some names that have names drawn through them. "Theldrick," "Loris Raknian," "Faceless One." The ledger gives only one entry for Maskholm: "Ilthane—Traitor’s Graves."
If you give this list to Manzorian or his allies (or some other powerful force of good), that will make it possible to eradicate the cult entirely. That is worth 30720 xp and two hero points each.
Valgrim pats Friar on the back, "Great job, man! We can put an end to the Cult once and for all. That Raknian fella is still out there, so we must be wary. Let's get out of this dungeon. By the way, Bubba. Any clue as to what the Traitor's Graves are?" Knowledge Local, maybe?
Valgrim packs all the treasure in the bag of holding.
Since Air Walk has 140 min duration.. Valgrim nods to Bubba and they start "walking" back up the shaft back to the Sinner's Sanctum and the elderly woman to ask her about the Traitor's Graves.
"Yes dear. Did you find anything down that nasty hole? I bet it had better stay down there, whatever it is. Nothing good ever came from underground. Just put the rug back, that's a dear."
"The Traitor's graves? Why, what on earth would you want to do with such a nasty place. That's where Lord Midas used to crucify his enemies. Horrible thing to do to someone, but I am told they deserved it. It's an island, right outside town. You can even walk there at low tide, but as I said, why would anyone want to go there? Such a nasty, nasty place. Probably damp and unhealthy too. May I offer you some herbal tea before you go?
Her herbal tea smells downright horrible, so you'd probably be wise to decline.
After Vug drinks her foul tea, Valgrim speaks to the party out of earshot of the old lady. "We can head to the Graves now or leave that for tomorrow and head back to Manzorian's. I have a feeling he and his allies are going to love this ledger and we also have items to sell. Friar can wind walk us there and we come back to Maskholm in the morning."