Three Days to Kill

"Deeptown lies in the shadow of mountains, a town where anything is for sale if you can only meet the price. But in the wild surrounding valleys of the Deeps, it's the bandits who make the darkest deals - and their ambition comes at a cost far greater than the contents of any wayward caravan.

You and your team have just been handed a new job: disrupt a meeting between a bandit lord and his mysterious new allies. At a remote mountain villa, you will strike hard and fast and leave terror in your wake. They give you the tools. You provide the talent. Survive, and you'll be well rewarded. Fail, and you'll pay the price.

You've got three days to raise some hell."

This was one of the first third party adventures under the OGL for 3rd edition published by Atlas Games under the Penumbra line.
The attack on the mansion is not a dungeon crawl, but feels like a commando raid aided by some unique magic items.