They appear to be non humanoid, multiple limbed symbiont organisms (though only a minority are symbiont with a Leviathan). Besides this not much is known about their physiology, only that they have the ability to join with a Leviathan (a biomechanical living starship), have superior healing abilities to most humanoids and possibly limb regeneration and that they can live in excess of one thousand years (however if they join with a Leviathan this is shortened to roughly three hundred years).
Separation from a Leviathan normally leads to both the death of the Pilot and of the Leviathan itself, though the Pilot can be joined with another if they are removed fast enough.
Not much of their culture is known, other than that they have a long history with the Leviathans.
Members of their species are only allowed to join with a Leviathan if they are older than three hundred years, as joining with them significantly shortens their life span by many centuries. There is only one known exception of this rule and that is the Pilot of the Laviathan Moya, who is known to be younger than the standard age.
When joined with a Leviathan the Pilots place the lives of the ship and the crew (in that order) before themselves.
- Farscape (First appearance)