So I'm the cousin, after the events of retrieving his loot we headed back home to make a harpoon. We ended up heading out again and as soon as we got out of the Black Forest to hunt the serpent it started raining, almost instantly the serpent apeared. Sooner or later we dragged it back to land on in the black forest and deafeted it. We had our revenge, made a serpent shield, and had gained gained too much confidence because right after we headed out to kill another. Believe it or not another one apeared sortly after leaving the Black Forest again but we were slightly further than we were before, So we ended up trying to drag it to the spot we killed the first serpent but didn't make it. All was lost, the boat broke, We died in the water, and now the serpent is gaurding our loot. Any tips?
Source: https://www.reddit.com/r/valheim/comments/sq2ayt/update/
