Originally posted by RequiemsRose:

The downside with raids in multiplayer is that the raid progression is based on the current highest player progression (as in, if your friend is already up in the mountains when you are just starting, you can get raids well beyond your current progression because SOMEONE on the server is that far along, even if it isnt you specifically).

To clarify, a new type of event becomes possible when a certain opponent is killed, be it a troll or wolf for example or one of the Forsaken. So just because someone has made it up a mountain, it doesn't immediately make it possible for drake event to occur, even if they have killed many drakes.

Here's the mostly up to date and complete list of events, which contains spoilers and everything: https://valheim.fandom.com/wiki/Events