Esketh is a lean human man with a narrow, severe face and carefully groomed black hair combed straight back from his brow. A smooth wooden mask covers the left side of his face, carved in the expressionless likeness of a calm scholar. Its polished surface bears tiny brass pins, ink-dark grain, and several handwritten symbols copied from arcane diagrams. His uncovered skin is pale and dry from years spent indoors among dust, candle smoke, and old parchment. He dresses in layered charcoal robes, keeps his sleeves impeccably clean, and wears a leather case of quills and spell components at his belt. His eyes are alert, cold, and constantly measuring.

Esketh is quiet, intensely observant, and relentlessly analytical. He speaks to people as if they are texts that can be annotated, categorized, and discarded. He rarely raises his voice, preferring precise insults and unnerving questions. Beneath his controlled exterior is a simmering hatred of helplessness, expressed through obsessive study and a constant search for methods of control.

Esketh van Thurn was once the promising youngest assistant in the private observatory of a reclusive arcanist. He was fascinated by the clean certainty of formulae and the promise that every mystery could be reduced to a pattern. During an experiment involving reflected starlight and a spell meant to reveal invisible writing, a containment mirror fractured. The accident left the left side of his face permanently disfigured and destroyed much of the observatory. Esketh survived, but the pity of his colleagues and the horror in strangers' eyes taught him a lesson he never forgot. He commissioned a wooden mask and began treating his own emotions as another dangerous weakness to be sealed away.