One of the most interesting things about Warhammer 40K is that the Chaos Gods are not really the opposite of virtue.

Khorne begins with courage, Tzeentch begins with intelligence, Nurgle begins with endurance,Slaanesh begins with beauty and pleasure.

The problem isn't that these things are evil.The problem is what happens when they become ultimate.

A virtue detached from any higher purpose doesn't remain a virtue forever, It becomes a monster.

That's one reason Chaos feels so psychologically convincing, It isn't temptation toward obvious evil,it's the temptation to make a good thing into the highest thing.