This page details how to complete the Marais-Vernier mystery in Evresin, Francia, Siege of Paris DLC.
How to Complete the Marais-Vernier Altar Offering
The Marais-Vernier offering altar can be found in the northern part of Evresin, near the coast. You’ll find the altar beneath a large tree in marshland. To make the offering, you’ll need to collect 3 Brown Trout (big) and 3 Seal Tails. You won’t need to go far to get both.
Where to Find Brown Trout (big)
There are plenty of big Brown Trout in the waters surrounding the tree and the altar. All you need to do is use Odin’s Sight to highlight their location, then shoot them with your bow before looting the corpses. You can also just use your fishing line if you’re not in a rush, but this will definitely take you more time. Be sure to look for the larger fish, which tend to swim alone, while the smaller fish swim in shoals.
Where to Find Seal Tails
To find the seal tails, you’ll need to travel a bit further north from the altar offering. There are numerous seals around the beach here, especially around the shipwreck. You should plan your attack carefully, however, since they will flee into the sea once you approach them. Try to shoot 3 seals quickly and then loot them for the tails before the entire colony escapes into the sea.
Once you have all the materials, return to the altar and make the offering to complete the mystery.