When you start a world you have the Eikthyr rallying the forest to raid you, every time you put a bosses trophy on the rocks a new level of raid is unlocked (might be from just killing them[i don’t know for a fact]). If you want a world where there isn’t any higher level raids just don’t kill/mount the bosses heads.
Maybe if you want a building world, or want to play with your children or someone still getting into games. Just thought it might be helpful
Lil edit, looks like when you kill the boss on the world you’re in, it sets you towards the raids you can receive towards your base. It’s not in a specific order, just when you kill a boss you gain a new raid tier. It’s when you put the trophies on the stones you get random generated spawns of those creatures associated with the boss. The boss ain’t attached to the character but the world. Which goes back to my main point.
Source: https://www.reddit.com/r/valheim/comments/rfbi4d/preventing_most_raids/
