Legend has it that the ancient Order of Ren was a force sect in the Unknown Regions known for their destructive behavior and lack of self control. They wielded the darkside like a hammer, though to them it was the power of the shadow. The shadow being the ultimate power in the galaxy.  Suddenly,  they vanished as if they hadn’t existed at all. There wasn’t even a whisper of the name, and they had faded into the oblivion of memory. 

Years later Siobhan Nuullic, newly released from the hold of the One Sith began exploring the Unknown Regions feeling compelled by something deep within the force. She stumbled upon the only remaining whispers of the Knights in the darkest parts of the unknown. Within the depths of an asteroid filled with the horrors of millennia, she found the final remains of them. A lightsaber,  a mask, and a single paragraph written in the language of the Ancient Sith. It read as follows......

Philosophy of Ren

The Ren doesn't stop to worry about what it's burning or the right or wrong of it, or the goals it might achieve. The Ren just is. It lives, and it consumes, and it doesn't apologize. It is its nature and nothing else

Power is the shadow, and worship of the shadow. It bestows it’s gifts on us with every swing of the saber and life taken. Honor to the shadow is paramount, and those who cannot touch the shadow cannot know Ren.

With these words The Knights of Ren had been reborn. Founded on this philosophy and adhering only to the shadow. Because to the Ren, no power is beyond that of the shadow