Luehmani summons a demon.
She expected a daemon.
It's an old ritual, an old circle, pulled together from ancient plains-lore and stolen tomes. The circle is drawn in honey, mixed with the ashes of burned out fires and the blood of ravens. It was meant to summon a powerful Slaaneshi daemon.
But the plains-lore is forgotten, and the she misunderstood the tomes. She draws the wrong kind of circle. She summons a demon, with no bindings, no protection.