Eidelon

Eidelons were once a highly advanced species of peaceful humanoid aliens in the Farscape universe.

Physiology
Their physical appearance was similar to that of Terrans and Sebaceans apart from grooves on the face and head.

Eidalons had the ability to manipulate others through some extra-sensory means and the ability to rapidly absorb information in an extremely short amount of time, using an eye-shaped organ concealed within their heads (the reason for the grooves, as the head opened up to reveal this organ).

Philosophy and Culture
They were an exclusively peaceful race, believing violence to be degenerate, and desired to bring peace and order to the galaxy.

History
The Eidelons are known to have been in existence at least 27 thousand years ago, during which time they made it their mission to bring peace and order to what they deemed to be a chaotic universe.

However, despite their peaceful overtures, they were frequently met with violence and aggression, thus leading them to the creation of the Sebaceans and the founding of the PeaceKeeper corps, which they used to not only protect themselves but instigate peace through "other means".

They mysteriously disappeared several thousand years ago, leaving their disciples the Sebaceans to keep the peace.

Re-appearance
During the finale of the PeaceKeeper wars the Eidelons re-emerged and with the help of Kryton tried to end the fighting between the PeaceKeeper forces and the Scarran empire (who until this point were uncharacteristically using diplomacy to claim worlds, but had since moved on to simply taking them) but to no avail.

The few remaining Eidelons were besieged by the Scarrans until Kryton, at the demand of the Scarran-Sebacean hybrid Scorpious, fired the worm hole weapon and ended the PeaceKeeper Wars.