0.8.2b. After killing the Abandoned Kerfur, I'd get an error message saying the following:
Warning: the object murderKerfur_c_2147294423 has detected a negative event! Report to the bug forums the sequence of your actions! Event variable has been set to 0.
I'm not sure exactly what steps I'd talk about here. I spawned in Abandoned Kerfur using the 6 meat piles and attacking my Kerfur Omega, then I fought the Abandoned Kerfur without taking any damage.