Evil = Misunderstanding Dharma
Dharma is the principle of the universe: attraction (desire), repulsion (aversion) and inertia (indifference). Evil knows this law, and uses it to ambush minds that are easily trapped by likes, dislikes and indifference. Evil feeds off our reaction: we can see this in the world every day, at every moment.
However, evil cannot understand emptiness, and the conduct of compassion. Evil thinks emptiness is nothingness, nihilistic and pointless as it has nothing to gain from the reality that is free of hopes and fears.
Those who misunderstand Dharma become arrogant and lack compassion, crossing over to the dark side. ReadingDharma is not the same as living Dharma. The devil’s disciples come close to realisation, but then claim it and get carried away, infecting others!
Goodness knows the complete picture as it does not see through a glass darkly, and realises that everyone, at some point, will understand the truth of our reality of pure consciousness.
Saying this, evil shows us the path through our reactions.
This is why evil/Mara can never completely succeed.