I somehow captured the Wisdom's Asp in such a manner that it got stuck threading between the mirrors, so it's half alive and half dispersed, half in the material realm and half in the Warp... it's not going to be able to reform like slain demons usually do, not while the box exists. Unfortunately the method wouldn't work safely on anything but a Wisdom's Asp..." You frown at a sudden thought. "Unless there's other types of warp entities out there that use untainted winds... anyway. It'd have to be a very, very unlucky or extremely stupid entity to get stuck in this exact manner."
"A shame, but considering the cost, it's unlikely that the same method would enter a Witch Hunter's standard arsenal. Still, once your studies are concluded, if there's nothing unusually sensitive about the information have it written up and sent to the Archives in Altdorf. Undistributed knowledge is wasted knowledge."