How can I darken the screen on a map?

Good afternoon, friends. I'm trying to make the screen appear darker when the character enters a cave, with only one light following him (as if he were carrying a lamp), but it's not working out well. The light doesn't stay centered on the character as it should. Does anyone know how to make everything appear darker when entering the cave, and then have the light return to normal when leaving?

https://preview.redd.it/khf56q37wvdf1.png?width=543&format=png&auto=webp&s=d84334777868c988637a7ca873c46b31d2edf12b