Based on the 5th edition adventure Tomb of Rakoss, updated to 6th edition
The PCs were sent north of the pass several miles to an abandoned complex. The PCs entered the complex and found it to be a well laid out complex carved out of the mountain. They also found it to be invested by several undead. The were first attacked by a animated stone statue. The were able to defeat it. The fought several mummies and skeletons as well as giant ants.
The fought their way to the largest room in the complex where they located a secret door that lead to a cavern complex “behind” the first complex. There they fought a manicore and some wolves. They located a cache of gold and items as well as the dead body of a magic user.
They found a several magic items and over 2,500GP. The party was able to keep all the items and gold