Since The Beginning, the Universe has feared death. All living beings will eventually die, hundreds of thousands of souls fade away every day, so many that long before creatures with vertebrae were even a distant thought, Lady Death relied on the help of beings that even she didn't fully understand.
She doesn't know where we came from, just that we appeared when she needed help the most and have stayed by her side ever since.
She has done her best to care for us. She gave us names and protected us from the other deities who had less than kind intentions. She crafted cloaks that allowed us to go wherever we needed to be, gave us tools to help gather the fading souls so we could bring them back to Lord Life.
He called us 'the soulless'. He seemed fascinated by how we could exist without him having made us. At one point, he wanted to 'see what makes them tick'. Lady Death did not like whatever that entailed and protected us by claiming we were her children and should Lord Life harm us SHE would bring ruin to the world he was putting so much work into.
Time passed and yet we did not age. Lord Time was confused by this and Lady Death claimed it wasn't her doing... but admitted she could not sense our life force fading. Lord Life claimed we had no 'life force' to begin with.
They were deities, immortal and all powerful. we were just strange 'soulless' beings who had literally just appeared out of the nothingness that had made up their world. Eventually, the question of what we were and how we came to be was decided as unimportant... mostly because we did not know and none of the Lords or Ladies were able to figure it out even after eons of thought.
We watched as life made its way out of the water.
We watched as meteors and ice destroyed the world.
We watched as humanity took their first steps.
We are the Collectors of Souls, the Guardians of the dead and dying, we are the children of Death herself.
We are The Grim Reapers