The warning hex (incantation: praecipio) is a hex that, when cast on an object, informs the caster of any intruder in the area that the object is placed in. It is the magical equivalent of a house alarm.
When Jesse Alexander came to visit the wizard Beifar Mahgo's house, a warning hex that the wizard's cousin, the witch Ana Mahgo, had set on the house warned her of his intrusion, and she popped over, wand at the ready. However, she quickly discovered it was only Jesse and then became embarassed. When Miracle Mahgo, Beifar's wife, asked her why she was there, Ana reluctantly revealed that she had set the warning hex on the house the last time she visited, because she was concerted for the family's safety. She cast it upon a plaster gargoyle figure inside of Beifar's home office, and when Jesse was found in the backyard, it warned her of danger, and she popped over. Miracle, who usually prohibited magic at the house, due to her and Beifar's children seemingly being Folk, surprisingly found it sweet of her, and even cried.