Originally posted by FRiENEMY™:

What mod is it?

UnrestrictedPortals[valheim.thunderstore.io]

There's a similar one from the same maintainer, but hasn't been updated in over 2 years. Mind you, this one also hasn't been updated in a year, so it might have issues with the current game version. Use at your own risk.

For managing mods from Thunderstore (because Thunderstore's own manager is neither maintained or distributed by themselves):

r2modman[valheim.thunderstore.io]