The instance of Beneath is once more available by virtue of memory given form! You will find it within the Dyisen-Ashtan Memoryscape from a ferry at v71389 - the same location you take a ferry to get to the Portent instance. Simply BUY PASSAGE TO BENEATH once there.

Penned by my hand on Falsday, the 13th of Ivolnos, in the year 0 AC.