Place it near the end of a dark fantasy edit, after the build and just before the final reveal. Put Inception Horn first to raise the stakes, then let this clip deliver the turning point, and follow it with Enemy Spotted to keep the threat alive for the next scene.
About this sound
This is a roughly 3.6-second spoken line delivered in a deep, grave narrator voice as he declares that great is the weapon that cuts on its own. The slow, weighty delivery feels grim and ominous, like a warning before a battle turns against you. It comes from Darkest Dungeon, the gothic dungeon-crawling game.