What distinguishes a psychopomp from an angel of death or a judge of the dead is function rather than character: the psychopomp escorts, and does not decide. Anubis conducts the deceased to the scale where the heart is weighed, but it is Thoth who records the verdict and Osiris who presides; Hermes leads shades to the Styx, but does not rule on their fate. This separation of roles, guide, judge and destination, recurs often enough that its absence is notable: Azrael in Islamic tradition merges the taking of the soul with its onward conduct, collapsing two roles most traditions keep apart.
Psychopomps are also persistently liminal figures, associated with crossroads, rivers, doorways and thresholds, the geography of in between places rather than of either shore. Hermes is a god of boundaries generally, not death specifically, which is part of why he can also serve as messenger and trickster; Anubis presided over embalming, the physical threshold work that prepares a body to be conducted at all. The concept crossed into twentieth century depth psychology through Carl Jung, who used psychopomp for a dream or therapeutic figure that guides a person toward unconscious material, a usage that keeps the structural meaning, guiding across a threshold, while discarding the literal journey of the dead.