Introducing a new race to the Paradoxverse: Umbralites.
Umbralites are basically shadows that were separated from their casters (yes that is what I'm going to call things that cast shadows, it's cool) and gained sentience. This can happen for any number or reasons, from magical intervention (i.e. someone purposely severing their connection to their shadow) to the destruction of a caster that is so sudden & so devastating that the shadow is the only thing left of them. Also, a caster is literally anything capable of casting a shadow. Theoretically, there can be an Umbralite whose caster was a rock, or a tree, or a library, etc.
Umbralites have control over their shape and can morph at will (making them a variety of shapeshifter). Some Umbralites prefer to stay in a form exactly like or reminiscent of their caster, while others like experimenting with their shape or maybe even hate the form of their caster & try to appear as different as they possibly can.
When an Umbralite is born, they're kinda stuck as a two-dimensional being for a while, but with time and effort, they can learn to become three-dimensional. It is also possible for an Umbralite to temporarily possess & control a caster not bearing a soul (i.e. dead bodies, machines, inanimate objects, etc.). It takes a lot of effort, though, and unless they are magically bound to the caster, they will eventually be pushed out.
It bears mentioning that Umbralites are not capable of casting shadows.
They can, of course, travel through shadows, and do so much faster than most traditional means of transportation. They cannot bring objects with them when traveling through shadows.
Although with some effort Umbralites can interact with the world as if they were corporeal, it's much easier to impact thing by interacting with shadows (like pushing a shadow cast by a box in order to move the box).
They don't need to eat or drink, but rest is required after expending a fair amount of effort.
Umbralites are masters of mimicry, and do not forget anything without magical intervention. Just as they can mimic the shape of any caster, they can also mimic the movement, mannerisms, and voice.