DND 5E What are the "hellscape" "underdark" campaigns, official publications and some popular fan-publications?

I'm wondering how extensive the campaigns have been for "hellscape" and "underdark" campaigns, where adventurers entire landscape is technically deep underground or part of some oppressive "evil" realm with demonic warlords as a regular threat.

I'm halfway remembering a CBR article (or even multiple articles) about these type of campaigns, including higher-level demonic villains and creatures, but I can't seem to put a peg on it..