I recently started playing Core Keeper, which also has portals. However, portals in Core Keeper are not 'plop and go'. After being placed, they must charge up for 20 minutes before passage is permitted.

I think Valheim could benefit from a similar feature. Once a portal is placed, you should need to charge it up with some special ritual that consumes some rare items. Maybe even use surtling cores as fuel for it. One passage = one core consumed.