In Chapter 4 you are requested by Celeste to come to the Cusp of Sunrise and meet with a "venerable, cursed dwarf" named Davdek who is looking for his lost son, Zenith.
Truth is, Davdek is really a doppelganger who is setting up the PCs to get Davdek for the Cagewrights.
Also, the truth is, Celeste is really a ghaele eladrin in disguise who knows something is afoul but cannot directly intercede and so becomes a benefactor to the PCs.
Ghaele eladrins have True Seeing as part of their usual prepared Cleric spells. Exactly why she failed to see Gortio for what he was is beyond me. Were I Celeste, I'd make sure almost anyone I met I would inspect with True Seeing, heck, I'd use most of my higher level spell slots just for that spell, in fact.
Of course, it cannot see through mundane disguises so maybe her Spot check failed to beat Gortio's Disguise check minus the +10 bonus from shapeshifting.
Thankfully, at least Vhalantru's simulacrum suit wards against True Seeing. Or that would have been awkward LOL
|Grogg of the North|
Celeste can appear strange to a DM reading the adventure for the first time. But let's consider a few things.
1) Gortio isn't a standard Monster Manual doppleganger. He has class levels. His disguise could be just as elaborately mundane as it is part of his alternate form class feature.
2) Zenith does have a father named Davked. And much of Gortio/Davked's story is true.
3) In the cases where Gortio/Davked lies or bends the truth, his Bluff modifier (having previously cast glibness) is a whopping +54! Even Celeste's +16 Sense Motive doesn't stand a chance against that. Given that, why would Celeste be suspicious enough to cast true seeing on an old dwarf who wants to reunite with his estranged son?
4) Celeste is a relative newcomer to the scene, having been summoned by Tenser to look into the activities in Cauldron. But while she is already suspicious of Vhalantru, it is never described as more than suspicion. Gortio is Vhalantru's crony, but Celeste doesn't necessarily know that.
5) If we give Celeste the benefit of every doubt, then she knows exactly who Gortio is and what his intention is. It doesn't even matter. The AP states that she does not want to reveal herself yet, but rather is trying to goad the evil forces in Cauldron into revealing themselves. Why? Who cares? She's a celestial being with an eternity to look forward to (if the PCs rescue her later that is) and probably doesn't think the same way mortals do. At any rate she wants to get Zenith out in the open and needs the PCs to do that because she doesn't want to overplay her hand.
I thought it was a little strange many years ago when I first read it, but it made enough sense from several angles to satisfy me after further reflection.
I eliminated Gortio and just made it the real Davked. Lord Vhalantru wants Zenith because he's a shackleborn but doesn't want to go through the trouble of extracting him from Bhaal-Hamatugn. So he introduces Davked to the party. Besides, Vhalantru is always pushing heroes hoping they'll die in some grand attempt at derring-do.
After Zenith is retrieved, the party moves on to the next adventure. Zenith is a shell of a dwarf anyway and Vhalantru can scoop him up for the Tree of Shackled Souls anytime he wants and, most likely, the party will never hear about it until they see his husk in the Tree itself.
This removes the hanging chad of Celeste and precludes any bodacious Perception checks from the party penetrating Gortio's disguise.