Task: Question Answering
Input (English): Passage: Abandoned by their father deep in a forest, young Hansel and Gretel enter a gingerbread house and are captured by a cannibalistic witch. The witch forces Hansel to continuously eat candy to fatten him up, and enslaves Gretel by ordering her to prepare the oven. The siblings outsmart her and incinerate her in the fire of the oven. In the fifteen years that follow, Hansel and Gretel become famed witch hunters, slaying hundreds of witches. The pair find that they are somehow immune to spells and curses, but the incident in the gingerbread house has left Hansel forever changed with a form of supernatural diabetes. He needs a shot of a insulin potion every few hours or he will get sick and die.Now adult, witch hunters Hansel and Gretel arrive in the town of Augsburg and immediately prevent Sheriff Berringer from executing a beautiful young woman named Mina for witchcraft. Mayor Englemann tells the crowd that he has hired the siblings to rescue several children presumed abducted by witches. Berringer hires trackers for the same mission in the hopes of disgracing the mayor and cementing his power. All but one of the sheriff's party are killed that night by the powerful grand witch Muriel, who sends one man back to the town tavern as a warning to the locals. Hansel and Gretel, along with the Mayor's deputy Jackson, capture the horned witch and interrogate her. They discover that the witches are preparing for the coming Blood Moon, where they plan to sacrifice twelve children to gain immunity to fire, their greatest weakness.
Muriel, accompanied by her witches and a troll named Edward, attacks the town and abducts the final child. Muriel kills Jackson and launches Gretel out a window, rendering her unconscious. Gretel is rescued by Ben, a local teenager who is a fan of theirs and plans to be a witch hunter himself. Hansel grabs onto a fleeing witch by her broomstick, but falls and is lost in the forest. 
Question: Which person tells the witches are preparing for the Blood Moon?
Output (English): Muriel.