I kind of think the reason why the Book of Life is referred to as 'extreme' sanctions and why they haven't used it yet is because it's intended to be an absolute last resort, due to how badly it may mess up the timeline. Butterfly effect and all that. And they'd be looking at potentially undoing/rewriting 6000+ years of history. Who knows what life would be like for anyone if humans never left Eden. I mean. No death and no suffering, obviously, but no free will or knowledge, either. But it WOULD accomplish the basic plan everyone knows God has laid out- create humans that live eternally in paradise. I'd imagine using the Book of Life is very risky and they can't account for the full extent of the effects, but I don't think that would stop the Metatron from using it as a means to make Aziraphale go along with the Second Coming. If anything, the chaos of that potential timeline might be even more of a motivator for Aziraphale to follow orders in this one.

that's a very good point!!!✨ definitely would fit the bill of 'extreme', but then again - if it is only used in extreme circumstances, as i said here and @aq-uatic reminded me in a separate ask, you'd think that the stopping of armageddon would be worthy of threatening the BOL, and yet it wasnt? or the fall of humanity, or even the fall itself... but somehow, hiding gabriel is bad enough to warrant erasure from existence...?

this does however only take into account how michael is threatening to use it (i.e. the extreme sanctions are not, in fact, officially sanctioned; metatron confirms this in ep6). michael takes the supreme archangel position, and presumably considers this to be adequate authorisation to wield the BOL as a weapon - something we don't see gabriel do in s1.

i would love to know what michael's rationale behind this was; jumping straight to erasure of existence for a fairly insignificant transgression. it might say more about michael's character than 'the true nature' of the BOL, but still find it interesting that for a reasonably cunning character, this threat is so... little thought-out.

and maybe that's just it; that the BOL does exactly what it says on the tin, and it's just michael getting gung-ho on their assumed new power and station. maybe gabriel never intended to ever wield this weapon because of the catastrophic implications it has (though this would bring into question what the point of the BOL is to begin with, if not to be used).

i honestly don't have much of anything to negate this from within the narrative itself, other than crowley saying that it was only a rumour (which i do think has some basis). but from a storytelling perspective, i do think it very odd that this new concept, this huge-ass weapon that heaven seems to have had in its back pocket all along, would be so blatantly explained and handed to the audience in s2. the whole thing, imo, just feels a little off.

biblically speaking, too, i feel that the BOL in the context GO poses is somewhat off too; revelation shows that the book belongs to jesus christ, and (heavily paraphrasing multiple references here but this is my understanding of the christian scripture on BOL) was for humanity to repent and enter the kingdom of heaven, or face erasure and be cast instead into a lake of fire in everlasting punishment.

now, of course, GO does not necessarily follow the word of scripture by the letter; but regardless, the whole notion seems odd in relation to angels. they... are of heaven; would erasing them from the book lose them their existence, or would it cast them out of heaven? by the same logic, does erasing humans from the BOL during the last judgement also mean those humans will cease to exist? the lake of fire is described as being "a second death" (20:14), but is that the same thing?

basically, anon - i don't know. idk if the BOL is what we're led to believe it is, but something in my gut (and by god has it been wrong before) is telling me not to take it as read!!!✨