Its pseudopsych bullshit, I think originally its the "Dark Triad" of Narcissism, Machiavellianism and Psychopathy, then the fourth trait to make it a tetrad is Sadism.

Its just a bunch of horseshit, two of those are literally whole separate diagnoses, and except for sadism they are all seriously complex collections of traits and interacting symptoms that cant just be boiled down to one trait.

Its also incredibly fucking suspicious that the wiki page for this shit has no section of criticism on this.