TLDR: Sailing off the end of the world could take you to a PVP server.
So I love the Co-Op aspect of Valheim and I love the way the devs have made this probably the best PvE survival game I've played.
I was thinking that at the end of the game, maybe there's a "Flying Longship" that lets you sail off the edge of the world. Doing so portals you to a collective PVP server similar to how sea of thieves has pirates meeting each other cross-servers. Maybe this server is just a small "Viking Fornite" style world for a quick game every once in a while.
This would be fun because
1. Its gated by the "Flying Longship", so only mutually equal vikings could meet each other
2. Death would take you back to your own server.
3. Your own base on your private server is protected.
There are currently 100,000 people playing valheim right now. I think some of the PVP servers probably accomplish this without the whole "Sailing over the edge of the world" but I thought the visual would be cool.
Source: https://www.reddit.com/r/valheim/comments/102f6sw/edge_of_the_world_combine_servers/