The origination of “the monster of the shadows” is in the “null world” where it was struck by non-null energy that that moved it to the non-null world. In this world, you need to survive, but how, you are getting weaker ever as the time flows. You find you get stronger by stealing “souls” you call it, that serve as you energy, your sole-energy. So you start hunting for souls and you find that you can also take over the bodies of the native creatures in this world, so you can survive the for you evil daytime at the cost of some extra of your sole-energy. You are not bound to the life of these bodies and will not die by their death, but you can’t stay in a dead body and will exit out of it anyhow if it dies. If it’s daytime then, it will destroy your sole-energy that will be exposed, and you will most probably die of it unless you’re fast… really fast. Therefore, it is important to keep the body living during daytime.

Use [W], [A] and [D] to controll
Use [I] to steal soles or to attack
Use [P] to posess and leave possession
Press [R] to start and restart

To posess a body, you will need a level of sole energy.
Some bigger creatures has a bigger amount needed to both steal it's bigger soules, or to pesess it's bigger body.
You can't stay forever inside a body, you can’t hunt soles from inside of it, only keep it alive, but be aware of the sun.