Death was born as Adelmar to the Creator, Opsino, and a human mother, Amalia. Opsino left Amalia once they found out she was pregnant. Amalia raised him by herself and Adelmar married a woman named Roza. They had a son who was called by Blanchard and a daughter called Grimhilt. He died at 28 after suffering from sickness.
After his death, he went to the Hereafter which only contained the two fates destined for humans. This included Eternal Bliss and Eternal Punishment. Heaven and Hell. Adelmar tried his hardest to enter both afterlives but he was stuck out in the darkness staring at Eternal Punishment which now seemed appealing. He learned how to create “matter” in the Hereafter and he created himself a castle. Soon, he learned to go back to Earth and he tried to contact his decendentsl but to no avail, Adelmar gave up anod killed someone to bring them to the Hereafter with him. He killed them with a weapon created in the Hereafter so the soul was locked out of Eternal Punishment and Eternal Bliss.
It then occurs to him that he can collect souls so he doesn't have to be alone. He started the Reaper Program. It morphed into something different but he was no alone anymore. He soon choose the name Death for unknown reasons.
Death disappeared and his castle was restricted to all reapers.
Death is locked away in his castle with no contact to any soul. He has been there for over 600 years but many Reapers still remember him.
Later in the story, he eventually returns after the human soul goes out. Things have gone bad so he must check on the Reapers and all the other souls.
Death hasn't been seen for centuries but records from elder Reapers have claimed he resembled humans and reapers. He was just as young as the rest of them.
Death is disorganized and freaks out about little things, or that is what elder Reapers say. He was friendly and acted like he was part of the general public, and he didn't seem to be any higher than the average Reaper. This personality made him intimidating and he never has understood why.