Dark souls

In a world filled with magic and beings beyond our imagination, everyone is born with with a number on some part of their body. The higher the number, the higher their magical power. In such case 40 would be deemed normal and a person with 90 would be deemed powerful. But our character is born with the number 0. Never has history seen such a low number, but through his journey, he discovers that he is actually very powerful, blessed with dark magic, magic never seen before in the world but few people know of him. He has a very tragic childhood. The technology used in this world are complex yet primitive. There are ranks for monsters in the world. Dormant being the weakest then forseen then awakened then great then demonic then colossal then fearful and terror being the highest. Their are also ranks for the mages in this world as f being the lowest then e then d then c then b then a and s being the highest. Killing a monster grants a human some magical power, increasing their strength and in some rare cases they might get something called a memory. Memory's are tools that the user can summon through their own free will. They have tiers on how useful and powerful they are as tier one being the lowest and tier 7 being the highest. And in even rarer cases some might even get a drop. A drop is the monster that they killed but the user is able to command and summon the monster anytime they want. Every monster has something called a core inside of them in if which the user obtains it, they can absorb it for some additional magical power or sell it. Memory's and drops are really valuable but you cannot rob them from the user and if you kill the user, the memory's and drops will simply be gone so the memory wielding person has to give them up with their own free will.