looking at the real world? A all the way. we can't get rid of nukes despite humans being able to take up other moral systems, there's literally no way the various outsider entities could team up for long enough to get something like that done when they are ontologically morally opposed to the core of their very beings.Assuming you're talking about gold piece value, I'd be valuing it in the context of the setting- and in the world (regardless of mechanical effect) that'd be an extremely powerful weapon. I'd have put it at the high-end cost of a Very Rare weapon or a low-end Legendary, which using A5E's pricing would put it at like ... 40,000gp? Is that the only thing it does, no +1/2/3? Yeah I'd stick it at 40k then. Maybe 50k. I wonder if this is the sort of weapon that would A. be used by Outsiders (3e's term for extraplanar entities) against rival Outsiders, or B. would be even more rare because all of the Outsiders worked together to locate and destroy them![]()
Is that the only thing it does, no +1/2/3?
I think that such a weapon could be useful for hypothetically bypassing DR & resist in 3.x and the immunity present in earlier editions but would have near zero value in 5e. Ive tried giving similar weapons in 5e while talking up the ability to kill despite regen when players were planning to fight trolls and the reaction was outrage that it might be needed when at will cantrips available to multiple PCs at the table did that automatically with no action economy or efficacy cost.How would you value a weapon that cancelled the various types of Restoration - so it would cause permanent death rather than banishment for extraplanar entities? Maybe to a max of CR 20.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.