Thanks for the thoughtful review!
The uncertainty is intentional, though I may not have made that clear enough in the text. The trials are not really meant to be clever puzzles. They are simple rites of faith and obedience meant for pilgrims who come in good faith. The PCs are thieves and impostors who only have the warning from the first chamber:
“Drink only when offered. Do not step over a serpent’s shadow. Do not speak your true name unless commanded. Kneel and be Judged.”
From there they have to read the rooms, decide what is being asked of them, and choose how far they are willing to go along with it. In the Hall of True Names, the tablet and stylus point toward writing a name, but for a group of thieves using false identities, giving up a true name should feel risky.
The real trial is whether these scoundrels can submit to the rites without their true nature coming through. They can also ignore the trials and try another route. The complex is open to the air, the walls can be climbed, and stealth is always an option.
The whole scenario is built around the fact that they are infidels sent to steal a sacred relic. In classic sword and sorcery fashion, they are in trouble from the start. Their best chance may actually be to take the pilgrimage seriously and somehow become worthy before they reach Zempra. Once they steal the Spine, the whole monastery turns against them anyway, and they still have to escape through three days of marsh while the monks and the great serpent hunt them down.
I'm working on a expanded Version of this module and I really appreciate your feedback!