This page offers a guide on where to locate and how to complete The Stink Brew, which is a Mystery located in Ledecestrescire, Assassin’s Creed Valhalla.
Collect the Viper Eggs
This mystery is located in the northwest of Ledecestre, off of the bank of the river. You’ll need to go beneath the bathhouse to get to the old woman who’s living underneath. She will ask you to get her viper eggs, and luckily for you there are an abundance of vipers in the surrounding area. There are several underneath the bath area and then a handful more on the riverbank near the underground entrance. When you kill them, you’ll be able to loot their bodies for viper eggs and a few other varying supplies. You’ll need to first need to offer 2 eggs, then 3 and then 4 viper eggs, for a total of 9 eggs.
When you’ve given the woman all of the eggs, she will let out an enormous fart that will distract the people in the bathhouse area above. When you’ve completed the Mystery, you’ll also receive a key that can be used to unlock the door to the left. To get to it, crouch to head through the gap in the wall. There are a couple of chests to loot that’ll make the stink worthwhile!