Fluff for me and a friend's Home brew Codex that were cooking up(Hes been unavailable for comment for a while now). Tell me what ya think!
Its basically bringing a lot of fantasy elements into the 40K universe.
For the Codex in progress click below:
Overview of fluff
Hierarchy: The planet Tysalis is ruled by a group known as the council of 13. Each of the thirteen members is in charge of their own areas of study and serve as checks and balances to ensure no one member gains too much power or influence. When a power struggle breaks out within the thirteen the services of the enforcers are brought into play and the quarreling members are detained. The members remain detained until they come to an agreement or are put to death.
Terrain: The terrain on planet Tysalis is a chaotic mash up. There are stretches of barren wasteland, jungles teeming with an overabundance of life, towers of bone and sinew jutting up from within rends in the planet's crust, giant structures of metal and stone, miles of swamps crawling with disease and the rotted, deep oceans of black, laves of molten flame, and mountains of rock covered in ice.
Level of technology: The technological level of Tysalis varies from very advanced in the scientific areas to archaic in the ancient areas populated by necromancers and cabalists.
Creation of corruption: In an area of the universe mostly unexplored by the imperium of man was the planet formerly known as Bugh'ka. This planet was an ork home world rich in life and was in an constant state of strife. During a particularly brutal war a massive wave of Waagh energy washed across much of the planet causing mass amounts of heads to explode on both sides.
Noticing the amount of life lost on the planet during the energy wave, the forces of chaos decided that the planet was weak enough that they could establish a foothold on it and use it to open a new eye. Opening a small rift and sending in waves of daemons didn't impact the number of orks as much as it would have been liked, so the chaos gods conjured storms of hellish fire and rains of corruption and bile.
These storms successfully cleaned the planet of most of its life. The remainder attempted to flee the doomed planet to escape destruction. Before they could however the forces of chaos opened a massive rift swallowing the planet and the fleeing orks whole.
Resurgence: 1,000 years had passed with no sign of the planet having ever been there. Humans and Orks had fought over the 7 surrounding planets for generations, each time causing the area where the rift once was to slowly loose its solidity. Feeling that the struggle for a few ork populated worlds wasn't worth the expenditure of life it was taking to maintain their hold, the imperium viral bombed all of the contested planets.
The destruction of so many lives at once weakened the area enough that the rift was able to reopen and with it resurfaced the lost planet.
Sowing the seeds: Suddenly under assault from a daemon infested planet and already weakened from war with the Orks, the imperium had no choice but to fall back to a more defensible location. The planet was named Tysalis in memory of a courageous marine that sacrificed everything so that his brothers could escape.
The rift continued to stay open pouring out more daemonic beasts thus earning the name The eye of the beast.
For hundreds of years the surrounding systems were plagued by beasts spawned forth from the eye. With each passing year the space contested by the planet grew making supply lines crumble and colony planets corrupt and traitorous. Fearing what would happen if things were not put to a stop the imperium massed an army to cleanse all the corrupted planets and close the rift. The force consisted of legions of Space wolves, Blood angels, Adeptus mechanicus, and imperial guardsmen.
Cleansing the surrounding planets, the force closed in on Tysalis. Sensing the perfect opportunity to deal a massive blow to the imperium, the forces of chaos caused the rift to flare up swallowing the entire force then everything vanished.
Birth of the Defiled: Several thousand years later the imperium believing the area was once again safe began terraforming the planets destroyed in the Tysalis war. Approximately 500 years after successful terraformation communication from the planets suddenly went silent. Right before everything when silent there was a single garbled distress call. The call said that never before seen beasts had suddenly appeared on the base and were slaughtering everything. Some resembled giant humanoid wolves and others looked like twisted marines in ancient armor that ripped off their foe's heads and drank the blood that gushed forth.
A day later a single escape pod from a planet that had gone dark was found. Inside the pod was a beheaded corpse with a note attached to its chest by a giant fang. The note said "you left us for dead in that hell and now we've returned to make all of you experience the same hell we had to endure a thousand times over"