The Darkness Effect Strength slider description has a bit of an inaccuracy, which tells that
"Adjust how dark the screen can get during the Darkness effect (caused by mobs, potions, and more)"

When in reality, only the warden and the sculk shrieker are able to cause these effects during normal gameplay. The correct description might go like this:

"Adjust how dark the screen can get during the Darkness effect (caused by the warden and sculk shrieker)" or "Adjust how dark the darkness effect get (caused by the warden and sculk shrieker)"