I've started trying out a "new game mode", kind of a speed run.
Basic idea is to beat Yagluth as quickly as possible, but with specific rules.
You start with a world where you have whatever tools and materials you want. Now you equip your character and take them to a new random seed world. You are not allowed to farm any materials from the new world, you can only use what you brought with you. You cannot go back to get more materials. You cannot start encumbered. You can go back to your original world to repair equipment (that is the only allowed reason to go back). You can only farm things from the bosses, and the pieces needed to summon.
I've tried a couple times now, and I find it fun, but haven't won yet. Partly because I couldn't fit a pair of portals into my first couple attempts so a single death basically ended my attempt.
The fewest number of in game days wins. 🙂
Edit: Time stops when you hang the last trophy on it's hook.
Source: https://www.reddit.com/r/valheim/comments/nhc7m5/my_new_game_mode_what_do_you_think/