A portal threat (in a narrative) seems to assume that danger is only external to one’s own world. It’s just not realistic. And it has more in common with a simplistic and separatist worldview—that we will cordon ourselves off from all threats in order to be safe—than a truly good one (a godly one).
In the good one, the hero enters into the darkness and faces danger, even at her own expense, in order to save the rest of them. Or to save the ones on the other side of the portal. Or simply out of faithfulness to a godly call, which is just faith working through love.