Originally posted by Kraft51:

Raids are directly tied to the bosses, you get the Raid for your "next" boss only after defeating the current boss.

example, you can go basically forever on a map without ever experiencing any Raid other than Eikthyr Rallies Creatures. just don't defeat any bosses and you'll be good, only drawback to this is you won't ever progress into better tech (Pickaxes,improved armors, etc) by doing this.

Well if you play such a slow pace you can
* Let a troll with a log hit tin and copper for you so you can skip eikhtyr
* Farm the red slimes that can drop iron and make so a Iron pickaxe
* Search silver by luck (all 3-5 Biomes you will find Silver ore sticking out of the soil)
So it is possible to skip all bosses except moder, but you will need far longer this way
And it is extremly tedious and hard to do that