I have no ideas, help pls
Well, a power commonly associated with them is the power to create rain, wind, and other storm conditions.
You could base it off of the Kasa-obake, a Japanese yokai that is basically a spirit inhabiting an umbrella. In one story, one of these yokai showed up in a valley on a rainy night. Anyone who saw it were terrified and couldn't move their feet, so you could make it so that they only appear during rainy weather and everyone who sees it becomes paralyzed with fear!
Is the demon the umbrella or is the demon holding the umbrella?
Anyways I'd say that if it's a demon with an umbrella. The demon can levitate with the help of the umbrella and turns invincible when not in contact with the umbrella.
If the demon is the umbrella then I'd say that the umbrella(demon) is unique in its design and cause people to fight over it pr the demon was sealed inside the umbrella but the seal weakens for every hour it's touched by someone and the demon instead of escaping, it possesses that person and pretend to be a human