the black guardian can only be hurt during its recovery phase, and even then, is only vulnerable to "magickal attack". on the one hand this simplifies matters, but on the other hand, it gives us nothing to cross-check with.
the problem is that it's easy enough to say what does and doesn't kill it, but very hard to relate that to existing figures. recall that standard damage for magickal attack is as follows:
i couldn't make any link between these figures and what the black guardian actually takes. i couldn't come up with any set of figures that sounded pleasing either, although there are plenty of possible solutions.
here, all references to "killing" the black guardian, or how much damage it "takes", actually refer to the damage required to push it to the next of its three attack phases. as far as i know, all three phases take the same amount of damage, excess damage isn't carried over to the next phase, and BGs of all three alignments have the same energy.
i'm using the following shorthand for attack types: 3pt weak-alignment, equal-alignment and strong-alignment are A, B, C; 5pt are D, E, F; 7pt are G, H, I. mantorok attacks, in this case, just do the same damage as strong-alignment attacks.
what follows is just a list of all combinations that i know will kill the BG, plus a few that don't. note that any combination that does kill it proves two things: for instance, "AAAAAA" tells us that six A-attacks will kill it, and that five A-attacks won't kill it.
the best numbering i can come up with, which i don't find very plausible, is: BG energy 150; ABC 28/41/55; DEF 38/57/75; GHI 75/113/kill. i hope that someone else can come up with a better explanation for the observations below.
the following list is of combinations that kill.
the following list is of combinations that don't kill.