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And the plan falls apart and Insight starts to panic. She cannot see a solution, as she expected to have advance notice. Her backup plan was to carve a spell circle (much like ones used in traditional demon summoning rituals) around the Prisoner. Which would have lowered the mana usage and freed up some of her owls to face any other threats. But honestly, even if she tried at the beginning, being unaware of the danger right behind her determined the outcome of the battle. 

And now, the Prisoner is loose.