Blade demons

Blade demons are a rare class of demons that take the form of a bladed weapon, most commonly a sword but spears aren't unheard of and one case of an axe is known. These demons are very rare with only 25 confirmed to exist. Due to their rarity, very few people know they exist, and fewer still have seen one. Blade demons form when a powerful weapon is abandoned in an area with large amounts of magic residue in the air alongside the soul of God like power. It is also not possible to start this process manually, it must happen by accident.
At the beginning of a blade demons life they are no more than a nearly indestructible weapon of immense power that cuts through anything as if it wasn't there. The edge of a blade demon absorbs all that it touches, adding to its strength. As they absorb more energy and matter, they start to gain semblance of intelligence. At first this intelligence reveals itself as a minor boost to the wielders strength and agility. Eventually it's intelligence will turn into sentience. At this point, it is mentally like a toddler. At around this point, living creatures struck by it will burst into dust which swirls around the blade until its absorbed. Once it grows intelligent enough, it will wish to control itself, and most of these demons choose to do so by corrupting their wielders mind, absorbing their soul and consciousness and controlling their body like a puppet. The process of gathering strength continues until it is strong enough to create itself a body to control. At this point the life of the demon is no longer going to change. This is no quick process, taking an upwards of hundred thousand years, or as short as a few months. This is entirely dependent on the potency of the absorbed strength.
The durability of these demons is so great that not even the gods are strong enough to break them. These demons are not inherently evil, instead living multiple lives of varying personality and morality.