Shivirani

Evil races give someone the PCs don't have to feel bad about killing. Obviously depends on your party, but if they befriend the hungry wolf pack and negotiate with the bandits, then a band of definitely evil goblins gives the barbarian something to smash without worrying if they're killing little Timmy's dad.

Edited to add: And if "he's an evil race" is your only reason for them being a major villain, that's bad storytelling. About as bad as "yes they're going to help you because they're good," and not for some kind of benefit to them, monetary or spiritual or whatever.

The glowing sign would clearly show if the DJ was there

Depends on which RPGs you play. If I start talking about sacred geometry with no context, it makes it harder to figure out than if you know it's Pathfinder.

Dictionary.