Lord Arcus

An enigmatic and reclusive entity, Lord Arcus' existence would have eluded mortal knowledge if not for a single reference in an ancient Elvish text housed in the Grand Mausoleum.
That scroll, untitled but referred to by the Kindly Ones as the Conversations of Ilduin-i after its author, makes a singular reference to one of the Potentates of Hell speaking reverently about an entity named Arcus. He is referred to by Ilduin-i with a title meaning "ruler" or "lord"; and the shinigami speaking in this infuriatingly short canto described Arcus using a High Elvish word meaning "father" or "ancestor", and as having "protrusions" of bone. (The meaning of the High Elvish noun used here is debated, as it is used elsewhere to describe branches, antlers and wings: things that grow out of other things in many directions.)
It has become an article of faith among adherents of Kelemvor from this single reference that Lord Arcus continues to exist, and is the progenitor and distant, solitary ruler of the shinigami. The relationship between such an entity, who would antedate the immortal shinigami and the newly appointed, formerly mortal God of Hell is one of the central theological debates among the Kindly Ones.

There is no record anywhere of any mortal ever having seen or spoken to Lord Arcus, in the records of the Mausoleum or in any other library consulted by scholars of the underworld. The academic community and the community of faith alike were set ablaze by the report that Bishop Spritzer encountered an entity with a bony head and protrusions from its shoulders after having walked past the Lieutenants of Hell, which no mortal is previously recorded as having done (her perspective pictured left). Her Excellency did not claim to have spoken to Lord Arcus or to have heard him speak; at its highest, she indicated that she saw something consistent with the ancient description only momentarily before being exiled from Hell.
Some have taken that encounter as confirmation of Lord Arcus' existence, status and continuing involvement in mortal affairs; whereas others are agnostic as to its meaning or reject it outright as a fabrication or hallucination. Bishop Spritzer herself stood for nearly two weeks before the templars testifying under great extremity to extract through physical and magical means every last iota of information in her mind about what she may have seen beyond that stone door.

Insight from Kelemvor

In the course of her conversation with the God of the Dead, Vega gained some insight sought after for millennia by scholars of the Grand Mausoleum about the relationship between the newly appointed mortal-turned-God and the long-reigning progenitor of the Shinigami.  Kelemvor let slip that he had sought counsel from Lord Arcus about what to do in respect of the forthcoming Omnicide.  He noted that the advice was worthless because the Shinigami's motives are always inscrutable and they speak in riddles, but confided that it seemed to be Arcus' view that since all things must eventually be swallowed up in death, is not the place of Hell to prefer death to life, or vice versa, in any circumstance.