NHF – new heroes for Heroes V 3.1.

If the developers hadn't removed all the standard Lua functions, we could freely move mountains, but as it is – pfft!

Maybe try this:
The hero touches the portal,
activate the portal
make interactable
has the hero's position changed?
if yes, deactivate the portal
otherwise, activate everything within a 2-cell radius of the portal
make interactable
deactivate the portal.