When my boys were little they were afraid of monsters. I tried many techniques to persuade them otherwise.
I tried telling them if there were monsters wouldn’t I have included them in my many warnings:
Don’t go out in the road.
Don’t talk to strangers.
And if there were monsters:
Don’t open the closet there maybe a monster in it.
Logic passed them by they were just too young.
You can use this image on your bottle
I bought a spray bottle and put in organic lavender oil (a very calming scent) then I added water. Make the scent strong enough so your child can smell it easily.
I sprayed it around my children’s room after I tucked them in. I’d make a big production of it looking and spraying under the beds and in closets.
Problem solved … from then on bedtime was much easier.