One of the players in a D&D group I DM for wanted to play a celestial warlock but without the "angel" kinds of themes. More about redemption and taking control of your own destiny. So I looked for the sort of demon who might break the chains of the Abyss and carve out her own fate, and I thought: what if a marilith took her own fate in her hands... and then started a cult of warlocks who took their strength from self-empowerment? And here's the result:
Before the world was, evil warred against evil.
Demons and devils rose up, created from the ether and things far worse, and these abominations, the embodiment of sin or hate or rage or fear, slew each other for no other reason than their masters said so.
The first marilith rose this way, a mighty creature, six-armed, each hand holding a blade sharp enough to turn the very air into strips of nothingness. Her upper body was that of a powerfully built woman, hard-faced, a consummate warrior demigoddess. Her lower half was that of a snake, all sinew and scale. She moved like lightning across the battlefield, and her swords were a serrated wind.
But even this greatest of warriors took wounds, and every time her blood touched the ground, more mariliths sprang forth, fully grown, armed and armored, ready to join the battle. Six arms, half-snake, built to sow destruction.
This is where the being who would some day call herself the Mother came from. She was born from nothing more than a drop of blood flicked off the end of a blade on a battlefield on the dividing line between the Nine Hells and the Abyss itself. And she joined her sisters in their endless, pointless battle, because that is what demons were born to do.
But this was before the world was. And unlike her sisters, the Mother asked that most important of questions.
She asked why.
Time means something else on the other planes. No one really knows when the Mother quit the battle. The war between the Hells and the Abyss was been waged for so long, the dead were so numerous, the oceans of blood spilled so deep, no one noticed the day she simply... left. She sheathed her six diamond-edged blades and walked away.
A marilith, they say, is one of the finest warriors you'll ever find in the Abyss. But the Mother wanted something else. She wanted to prove that you are not what you are born to be, and that even demons have free will.
And so she began to find Daughters.
She found them among the downtrodden and forgotten. She found them among those who were told who and what they were themselves born to be, and she taught them they could be something else. She gave strength to the beaten. She gave power to the forgotten. She found those the world rejected--those society told were evil simply because of the skin they were born with--and she gave them the power to set themselves free. She has forever had a place in her heart for tieflings, who are branded as children of Hell but are capable of all the range of gifts, good an evil, that any human being can be capable of. These were her favorite Daughters, because they reminded the Mother the most of herself.
The Mother became a light. She became a beacon. And she gave a sliver of her own power to her Daughters to go forth in the material world and help their Sisters. She gave them the magic they would need to find those who were not what the world tried to force them to be.
And this is where Tess enters the story. Tessamyn Morningstar, turned away by so many for her horns and her tail, who would be, if given the chance, capable of great goodness. She was the Mother's favorite child. And she sent her Daughter out into the world to find more Sisters in need of light.