Due to an unusual set of circumstances (mainly the result of accientally embarking on a map with no iron ore), I was recently in a position where I had a goodly number of caged prisoners to execute. Being a lover of efficiency, I built a drowning chamber. Being dorfy, I used magma.
I anticipated some benefits to this approach. For one, I would likely not have to release the prisoners, as the (wooden) cages would not likely protect the prisoners as they would (mysteriously enough) against magma. The obvious drawback was that I would lose the cages, but I considered this an acceptable cost associated with causing this amount of fire, mayhem, and destruction. Of course, I would have to avoid using my nickel cages, as they are magma-safe.
Then, a happy accident occurred.
While the wooden cages mostly performed as expected (with the exception of one that freed its elk bird occupant before the magma later overtook it), the nickel cage I had accidentally placed remained in place, but its occupant was nevertheless killed.
Thus, I have discovered a way to:
-Kill prisoners
-En masse
-With magma
-Without wasting time linking mechanisms (magma-safe or no)
-And keep the cages afterward!
Sadly, as I did not set out to perform this experiment, I cannot yet say whether the goblinite would survive. None is in the nickel cage, but this is not proof either way, as I don't know whether the goblin carried any, and it could theoretically end up outside the cage. I will try to acquire appropriate samples in the near future. Meanwhile, in the interest of science and definitely not sadistic glee at all, I invite you all to independently verify these results so that they may be added to the wiki.
For science.