More of a waystation than an actual realm, the Patresilen is the home of the Lethen’al. It is not on earth; rather, it is a halfway point that is between creation (the Quain) and Heaven.
This is where they formed after their departure from Heaven as Aesari, the angels of the Creator. Their souls were fragmented, and shattered into millions of tiny fragments (called si’ru). These fragments were rearranged and combined with matter, forming the E’ine.
As they were beings cobbled together from other souls, the E’ine went mad as disparate parts of their new selves meshed together. But, they retained most of their angelic abilities, and the destruction they wrought was unprecedented. As they settled into their new selves and the time of madness passed, they created the city of Raqui and began to have children; these were the Lethen’al. In time, the E’ine and the Lethen’al left the Patresilen and entered creation (the Quain).
The Patresilen was forgotten, lost to memory and relegated to myth. It was not until the Apostate’s war that the way back was found and the Gates of Golorath created to connect the two realms. In their despair, the Lethen’al abandoned the Quain, and sealed themselves off within the Patresilen.