Okay, well that is interesting. Llyarden, I would assume that the essence left would normally migrate to that resonance area, and in this case is being blocked by the ward.

I would still suggest finishing the thing off. I don't think we can trust this thing as any sort of ally/asset, and there are probably much safer things to use with spirit bottle and the like.

In addition, safely containing this thing long term in the wards will require maintaining control over the area, which would be difficult enough if it wasn't about to become a crime scene with some pissed off and probably from now on hypervigilant owners.

We're safer eating the essence, dismantling the wards, picking up evidence of our presence, and bugging out before the sun comes up.