Darkening Specific Actors(background) and forcing depth of particles

[MM_WolfWin (WolfWin)]

Hey all! I wanted to try to recreate this darkening effect(using emmisive color on particles did not work well) where the background get darker while characters and particle effects remain the same brightness? Could I make a specific shader for the background elements?

Examplehttps://youtube.com/watch?v=xI3y5dJlKEU

Also how can I force depth of particle effects to be behind or in front of specific actors or all actors?
Example:

Tales of Vesperia: Definitive Edition - Forest of Keiv Moc Gameplay (TGS 2018)

Thanks in advance!