You Don't Want That
Joan leaned close to the sewer grate. She had to, to hear the Thing in the Sewer, who only whispered. "If you're sure you want one," said the Thing. "I'll grant you a wish. Choose carefully." She only needed a moment. "I want to be better than Danny," she said of her brother, "at everything."
"You don't want that," whispered the Thing in the Sewer.
"Yes, I do," she said, and the Thing acquiesced.
When Joan returned home, her mother told her of the accident. Horrified, dripping tears of mourning and rage, Joan returned to the sewer grate. "Fix it," she cried. "Bring him back!"
"You don't want that," whispered the Thing in the Sewer, whose home was becoming salty.
"Yes, I do," she yelled. "And stop telling me what I want!"
Joan returned to find her mother at the dining table, white with fear. Sitting across from her was Danny, throat mangled, jaw gone, bloodless rips in his shoulder and chest. Death clouded his eyes, but hate made them burn bright.
She fled back to the Thing. "Why did you do this?" Joan demanded.
"What did you think would come of making wishes to a thing in the sewer?"