General question: how do you design interesting antagonists for your campaign? I'm not talking about random encounters, but individuals/groups/monsters that have a more sustained presence and influence over your campaign, and that the PCs must content with. For example, the 5e DMG, in providing tables to help fill out motivations and goals for NPCs and villains (pp. 74, 90 and 94), does not primarily talk about good vs evil but suggests a lot more details and context to answer the questions, "what
kind of evil? Evil for whom?"
To borrow language
from another thread, I think antagonists that are evil-for-evil sake can be good zero-dimensional villains and perfectly valid for having fun. But if you want antagonists and a world that is more 1-dimensional or even 3-dimensional, you will need more than simply an alignment axis to detail the various factions, npcs, and plots going on.