There is evidence that they can possess people; and influence them.
They can possess people and give them power while devouring their souls.
What possessed people to move to Peaches in the first place?
He has the power to possess other people and his limbs often fall off.
He could possess people and enhance their aggressive behavior.
Why do you think there are so many stories of devils possessing people on isolated farms?
Astra - Female in blue costume who can possess people.
Capable of possessing people by feeding on the darkness in their souls.
The munin could "possess" people who had the talent for it.
However, it also gives her the capacity to possess other people; to reach so deeply into them that she can control their actions and emotions.