I ran This with a group of five 6th level players, and the start of the adventure is pretty good, every having a bit of an investigation, easy to improv from the info given. Then you get the first big fight, which was interesting and gave the party a few headaches. Then a smattering of lower level encounters may have increased their confidence and on to the Big Bad. The only way it wasn't a TPK at the end was by removing the SR and DR of the main antagonist. The party that took on the adventure was a sorcerer, two fighter, a rogue, and A druid (with a armoured Dire Ape Companion).
If you are thinking of running this as is, ensure your character have some sort of ability to hit with cold iron or good weapons.
