soul collector-contract with death

With this technique, you have the ability to summon souls, sort of like in solo leveling. You can also put souls into objects without one, like a tree. Then, when your close to death, the god of death appears with a contract, where you have to kill a specific number of people and collect their souls, which you can then use later as a sort of army. The only problem is if this is even a viable technique or not, so please let me know.