How does the maker of ruins kill?

[Tuidjy]

I was playing with Doom horrors, and came across the Maker of Ruins. It killed
a defense 50, 400+ hps unit in one round of attacks. It has four weapons. I
can see that they are area 1, and I assume that the effect triggers even if the
weapon does not hit. But even with a weapon that always hits, and cannot be
resisted by any means, I still do not see how it could have gone through 400+
hps. Any ideas?