Little is known of the origin of the Hand of Eris.  To call it an organization would not be quite correct.  Perhaps it was a cult, or some more loose affiliation of entities, gathering in the forgotten corners of the universe.  Although it was named after Eris, the Greek goddess of chaos and discord, and the Hand of Eris was her symbol, the actual group seemed to have little to do with the goddess herself.  Many members were practitioners of chaos magic, but many others were seemingly uninterested in supernatural beliefs altogether.  The group did seem to have some connection with the strange phenomenon known as chaos energy, although the exact nature of the link seems uncertain.

The Hand of Eris had little discernible structure as various leaders rose and fell from favor, and factions frequently split off, only to be reabsorbed later.  One of the more notorious leaders in the group was Dr. Ignatious P. Cyclone, who had been a brilliant, and highly eccentric scientist late in Era-0, before coming under the influence of chaos energy, and turning to a life of piracy.

The militant wing of the Hand of Eris was known as the Fractal Legions, and consisted of various groups that formed, dissolved, battled each-other, and generally wreaked havoc.  

Notable Fractal Legions included:

The Raging Schwa:  a band of berserk warriors who attacked at close range and didn't back down easily. 

Most members of the Hand of Eris were human (or at least started out that way), but it also became quite popular among a number of other species.  Even robots and extra-dimensional beings were known to have joined.

Throughout Era-1, the Hand of Eris consisted mainly of small, isolated groups with little power.  Still, the group came into regular conflict with the Planetary League, whilst sewing disruption and discord among the frontier worlds. 

During the Great Reckoning, as the Planetary League was crumbling, Hand of Eris activity spiked, and several planets became "Chaos Worlds", controlled by various factions of the Hand.  Throughout Era-2, the Hand of Eris frequently found its self in a state of outright war with the Holy Empire of Man, and the conflict was especially intense with the Empire's religious police, the dreaded Hamsa.

During the War of Galactic Unification, much of the membership joined the Galactic Republic, and it seemed to have largely died out during Era-3.