if you want your avatar to be effected by fog in any worlds with fog, all you need to do is go to edit, project settings, then set this to "manual" and check all 3. now your avatars will be effected by fog in any world under any type of fog.

https://cdn.discordapp.com/attachments/438554690351792128/483481372732948480/unknown.png

https://cdn.discordapp.com/attachments/468306723699032074/483446377234563073/unknown.png