Content Warning: Body horror (visual and text)
Death has never been seen by the living.
She is not invisible - the living simply cannot perceive her. From what the dead bring back as stories, some might assume the dead can't, either. Her appearance varies between person to person, becoming something more familiar to something they've seen in their time, but there are always similar features that show up, and they lend themselves to one theory - the problem with seeing Death is that she's far too alive to comprehend.
Death appears as a faceless bipedal creature, with her own organs floating about her - massive organs, alien and numerous, occasionally extending into infinity. Despite this 'affliction', she does not suffer, and despite her frightening appearance, she is calm, and not unkind. She has never sought to harm those who have seen her - only guide, or ask questions.
While the dead of Nskanetis wind up in the Leyline, spirits lost from Nskanetis or from other worlds tend to follow Death. Her reputation as a guide and association with ghosts follows her wherever she goes, and so do the dead. Sometimes she finds them a proper place to rest, other times she simply has a gaggle of curious spirits tagging along for a while.
She rarely appears on Nskanetis, and has a similar silhouette to Nskanetis Herself, creating some theories that the two psychopomps could be sisters, or separate manifestations of the same being. Perhaps Nskanetis Herself only appears as such in the leyline, appearing far more alien and less like energy elsewhere.