- "There are beings in the universe billions of years older than either of our races. Once, long ago, they walked among the stars like giants. Vast and timeless"
First Ones is the name used to refer to group of ancient races which inhabited the Milky Way galaxy billions of years before the rise of the current group of species. Even older than the First Ones is the race of biologically immortal beings known as the First Born, which influenced the development of the First Ones as the First Ones would later do to the younger races.
Billions of years ago, the majority of the First Ones and the few remaining First Born left the galaxy, departing to unknown territories. The Vorlons and the Shadows stayed behind in order to influence the evolution of the younger races, although employing very distinct techniques and goals, differences which eventually escalated into a full scale war using the younger, psychologically malleable species as weapons.
Another First One species, the mysterious Walkers of Sigma-957, appear to be a race of isolationists, but almost nothing is known about them. Of the remaining species that make up the First Ones practically nothing has been revealed. Other species known to be about as old as the First Ones include Asmodeus' species, the Hand and the Thirdspace Aliens, but it isn't known if they are to be considered First Ones themselves (however the Thirdspace Aliens, coming from an extradimensional realm, are almost certainly not).