It has no reality of its own in the sense that darkness is merely the absence of light. But the word 'merely' is deceptive. Creativity brings beauty and order into being, vandalism is a reversion to disorder. Falsehood and lies have no meaning except as the denial of a previously existing truth. Enslavement can only exist in relation to freedom.
Evil is nothing but the refusal of love and compassion.
But disorder, falsehood, lies, enslavement , and moral evil are terribly real and impinge on us to destroy all that is good in our lives. We can only define evil in relation to humans who are tempted, enslaved, deprived of dignity, unjustly accused, oppressed, abused, or denied love and compassion. We cannot think of evil in impersonal terms. Temptation is a voice suggesting another course of action, as when Jesus was tempted. Enslavement needs humans to do the enslaving.