Item from Overlord by Kugane Maruyama
The Slane Theocracy's World Item — a mind-control artifact powerful enough to brainwash a Floor Guardian, and the weapon that accidentally made Ainz aware of the greatest threat to Nazarick.
Downfall of Castle and Country is the Slane Theocracy's most dangerous possession — a World Item inherited from the Six Great Gods that provides absolute mind control. They used it to brainwash Shalltear Bloodfallen, forcing her to fight Ainz. The confrontation cost 500 million gold to resolve and was one of the most traumatic events in the series. The irony: the Theocracy intended to eliminate a potential threat. Instead, they alerted Ainz to their existence and possession of a World Item — making them a priority target for Nazarick's eventual conquest. Using their trump card was strategically catastrophic.
Its exact form is not widely described. As a World Item, it overrides normal magical rules entirely — no resistance check, no saving throw, absolute control.
Also known as: Downfall of Castle and Country