A myth, as Joseph Campbell once explained, is a story. Specifically, it is a story that a people tells to itself to explain something about how the people relates to the world. A body of such stories bundled together is a mythology. The effect of a mythology is to bring order to the minds of the people, simplifying a complex world into something easily comprehended and acted upon, much as adults do for young children.
To weaponize something is to take up a thing and employ it as a deliberate tool intended to do damage to those subject to its effects. Tree limbs wielded as clubs, rocks used as sling stones, language used to incite others to violence, diseases modified to maximize effects upon subjects, power sources used to project flame or explode on command, and so on.
"The Narrative" is the mythology promulgated for the purpose of providing cover--cultural, social, and political--for those seeking to take and hold power. It's method of operation is that of a parasite; it is a parasitic memology, and those affected become subjects of a hive mind. It demands adherence to group-think, loyalty to itself above all things, and feeds upon the anxieties and insecurities of those that it infests via the classic cult techniques of isolation, conformity, indoctrination via repetition, and trauma. It acts in the psychology of a rabbit warren, even if it presents itself as something other than that.
"The Narrative", ultimately, is a lie. It is the use of rhetoric, in the form of mythology (itself masquerading as something legitimate, such as academic discourse), intended to commit fraud upon a people for the end of seizing power and keeping it indefinitely. The sooner that a people see this for what it is, the sooner that they begin to resist it- and ultimately destroy it. To use "The Narrative" is to wage war.