This is one of the biggest mysteries in Elite Dangerous. The Formidine Rift is a part of space around 10,000 light-years away from the bubble located in the Upper 2 quadrant of our galaxy. The mystery possibly leads to the planet of Raxxla. The end result is located somewhere in the rift. It has been in game since version 1.0.
The story behind the Formidine Rift mystery was written by Drew Wager in his book called Elite: Reclamation, which is one of several books in his series on Elite. Wagar confirmed there's something there to be found in-game.
John Harper, author of And Here The Wheel, wrote in a Kickstarter comment:
"You don't know what I've seen. I've sailed beyond the Formidine Rift, seen the fleets of Octagonal ships blocking out the stars. I've stood on lost worlds, sterilised clean by the Thargoids and erased from humanity's maps. I've seen the graves from the Thargoid wars, countless headstones stretching beyond the curvature of the horizon, little spots of reflected light dottering the abandoned continent ..."
Commanders have been searching the Rift for years without much success up until the end of 2016. Then finally, some navigation beacons got discovered in sectors located in that area of space. Those beacons had encoded location coordinates which were quickly revealed to the public.
No one knows for sure what actually happened in the Rift. Commanders have been able to find a unique settlement down on one of the planets in the Formidine Rift region, while another has been found in Conflux.
Unregistered beacons near the heart nebula and soul nebula
|System||Message||Translation||Rally point||Time repeats||Notes||Links|
|EAFOTS LZ-H B10-0 D||dyjepqyuwludcqckj
|dynasty expedition beacon dnstys6erp003 rallypoint d1 formidine rift eafotsizhb100 mode standby||D1||15 minutes after each hour||Translated system name and system beacon was found in do not match. (i vs l)|
|EAFOTS EU-R C4-1||DYJEPQYUWLUDCQCKJ
|dynasty expedition beacon dnstys6erp003 rallypoint c2 formidine rift eafotseurc41 mode standby||C2||On the hour, every hour|
|EAFOTS GL-Y E2||DYJEPQYUWLUDCQCKJ
|dynasty expedition beacon dnstys6erp003 rallypoint 6 formidine rift eafotsglye2 mode standby||6||45 minutes after each hour|
|EAFOTS RA-G B11-0 3||30 minutes after each hour|