they use dark forces

"There's an anger in you," said the television astrologer Fergus.
"How do you know that Fergus?" I wondered on the verge of being stunned.
"I can see your aura. There's a flash of red in it."
I looked at him searchingly then smiled.
"No you can't."
"I can yeah. Your anger shows in your aura. It's shimmering there all around you."
"I've got a ratty little face, haven't I Fergus?"
"No, it's your aura. I can always tell from the aura."