What is the fear of demons called?

Daemonophobia

The fear of demons is called daemonophobia. It is a type of specific phobia, which is an irrational fear of a specific object or situation. People with daemonophobia may experience anxiety, panic, or even a full-blown phobia when they think about or see images of demons. They may avoid religious or spiritual settings, or they may only be able to tolerate them in certain situations.

The other options you gave are not the fear of demons:

• Domatophobia is the fear of houses.
• Dendrophobia is the fear of trees.
• Samhainophobia is the fear of Halloween.