Immortality was the state of living eternally, being deathless. The goal of many sentient beings throughout galactic history, the state of immortality was attainable by few.
Such individuals were calm and centered; at peace and existing in the present—in tune with the Living Force. Only through this, known as the light side of the Force, were individuals able to let go of their physical body, becoming one with the Force and manifesting their consciousness in order to commune with the living after death through the Cosmic Force.
Individuals fearful of their own end may turn to seek immortality, drawn to become obsessive for eternal life in their lust for power. Such individuals who were naturally highly attuned to the Force through high quantities of midi-chlorians in their blood—which formed a symbiote with their host as the microscopic life forms spoke the will of the Force—were consumed by indulging in emotions such as fear and hate in their attempts for immortality; forcefully tapping into the Force through their own—and in certain cases, others’—midi-chlorians. Known as becoming chained to the dark side of the Force, all who took this path, many a Sith, perished as a result of attempting to amalgamating and hoarding power for immortality.
However, phantoms of these dark side menaces existed. These spectres of the past haunted lost, lifeless lands, such as the tombs of Korriban. Preserved in physical objects, such as the Muur Talisman and Rakata mind prisons, vengeful spirits seeped out of their cages, always attempting to latch themselves onto a living body, hoping to take control of other life forms and accumulate power without end.
With such constant looming threats against all of life, the Jedi, servants of the Force in the galaxy, sought to bring balance; maintaining and restoring harmony among the Living Force. Through great sacrifice, balance was achievable, and with peace and purpose, one could retain their consciousness after death and also achieve immortality to continue giving to the living.
Although threats of power-hungry individuals reccured, it was through the teachings of the immortal that newer generations learnt, grew, and overthrow their darkness; there was a cyclical nature between the dichotomy of light and dark.