the Exopath Center classifies exopaths by three categories:

S-class: the exopath was deliberately created by a technopath (ie: NULL)

P-class: the exopath is the result of a technopath's mind lost in the æther, or some fragment of it, or a deliberate copy of a humanoid mind (ie: Sappho)

X-class: the exopath seemingly emerged spontaneously in the æther or its origin cannot be determined (ie: ÆON)