The three Prime Evils are the Arch-Leaders of the Axis of Evil.
Technically, only Asmodeus is a true Prime Evil, and it may well be that he is the last of his kind. Long forgotten lore holds that The Prime Evils were born when the first Prime Evil, Tiamut, the seven-headed dragon queen, was slain. From her seven heads a single entity arose, and divided amongst themselves. After dividing the immediately set to quarreling. This quarrel, now known as the Blood War was the single greatest upper-hand that all of existence had over the forces of evil.
Who all was born from that dividing is now lost or forgotten, but it believed that each of the Prime Evils represented one of the various darker Eidolons, with two representing the precursors to Tanar’ri. Asmodeus was the first Baatezu, or so it was said, and Demogorgon is the result of two of the Prime Evils coming together in a dark ritual attempting to recreate their Draconic mother. Infestix was said to be the first Yugoloth, and it is said that the aberration deity, Nyarlathotep, was among the prime evils. Who all specifically was born of this momentous event is unknown.
The three Prime Evils that have created the Axis of Evil are Asmodeus, Graz’zt, and Mydianchlarus.
Asmodeus, Lord of Terror
One of the oldest entities of all existence is alternately described as an evil god, a powerful devil, or a being of beyond-divine power. The strongest of the three Prime Evils of the Axis, he commands the forces of the Baatezu with a firm and strict grip.
It is said that in a time long forgotten, Asmodeus attempted to take over the realm by possessing the son of a well beloved king, and sewing corruption and vile-power under the mask of a horrible war between two long forgotten nations. Rumor has it that the powerful warrior who slew Asmodeus in this ancient time still lives, wandering the lands of Azuria, seeking heavens know what.
Graz’zt, Prince of Destruction
A former servant of Asmodeus, Graz’zt has been elated to the power of Prime Evil in a recent confrontation between him and the dual-natured former prince of abyss, Demogorgon. Graz’zt through intricate political arrangements and diplomatic exchanges set himself in a possition to defeat and consume the very essence of the mandrill-headed prince. There is no telling who would be more powerful between himself and Asmodeus; for Graz’zt was once a lesser, created by Asmodeus’s will alone, but now having consumed the power of two Prime Evils, he may stand greater than his former lord and creator. Then again, there is no telling how many Prime Evils Asmodeus may have consumed in time gone by…
Mydianchlarus, King of Hatred
The reining ruler of the mercenary Yugoloths, or daemons, Mydianchlarus is one in a long line of Oinoloth, the ruling class; a line leading back to Infestix, a supposed member of the original Prime Evils. Mydianchlarus is not only King of Hatred, but also master of many secrets; in fact it overthrew its predecessor, Anthraxus, not through violence, but by whispering a secret in Anthraxus’s ear so profound and disturbing that Anthraxus was compelled to leave all existence for eternity. Mydianchlarus was the first of the Three Prime Evils of the Axis of Evil to gain a Gifted Trinket, thus having full access to the Material Plane.