So are we all agreed that sawing....

[Juby]

The bull I think was used to terrorize (and increase vitae production) in the other victims waiting in the cells. Agrippa says Alexander uses the broken orb for torture as even a broken orb practically leaks madness. What I suppose that means is that the orb fragments being nearby were powerful enough to make the victim even more angsty.

Yeah the bull was not meant for vitae extraction itself, but to strike fear into other prisoners heart which might make vitae production more efficient. I believe it was meant to kill when a victim was no longer useful.