Evil manifests through demons including physical illness, mental impairment, false doctrine, lust and spiritual possession. John 10:10 describes Satan and demons are described as thieves who come to steal, kill and destroy, causing pain and suffering.
In Matthew 12:22-29 Jesus healed a man who had been deaf and mute since birth. The Pharisees thought Jesus used the power of Beelzebul, the prince of demons, to drive out the deaf and dumbness demons from the man.
Lucifer and the fallen angels spread physical disease. Luke 9:37-42 records the story of a young boy possessed with a demon who went into a convulsion when he encountered Jesus. Before healing, he engaged in self-destruction and mutilation.
Demons of lust and greed lead people into moral compromise. The apostle Paul warns against unclean spirits of deceit and false doctrine in 1 Timothy 4:1.