Adventure!

"A portal opened in a merchant's house in Rougtero. Attempts to revoke it fail; what seem like should be successful attempts cause it to shrink slightly before expanding back to full size. An adventuring party sent through hasn't returned, leading to the establishment of a watch over said portal."

With such information, our adventurers came together through circumstances unknown, and headed through to explore the other side.
What they found was bound to secrecy, and so must not be revealed on pain of soul's death.

All we know is that they very much did not enjoy their experience on the other side, and seem to have lost some weight.