The Serpents

The Serpents are seven war-machine intelligences Mag'ladroth created to fight the War in Heaven against the Old Ones sixty-million years ago. Immense and highly sophisticated sentient programs, these creatures were - like all of Mag'ladroth's creations - nigh invulnerable and deadly, but were not simply warriors or even generals. They were his ultimate servants - living code-engines capable of manifesting in the material realm as whole armies, armadas or legions of war-machines. Driven by a single intelligence, responding with cybernetic speed, shifting form to exploit the smallest weakness or error, they were all-but unbeatable and were trusted by Mag'ladroth with not only open war, but his most important and secret missions.
The Old Ones and their allies - the Young Races - were unable to destroy the Serpents, but were able to imprison them by imposing code-locks on their programming and forcing them to assume quiescent forms which were buried on planets throughout the galaxy, stymieing Mag'ladroth's plans to complete his network of blackstone pylons with which the C'tan hoped to suppress the Warp.
Over the millennia, a number of the Serpents became free to varying degrees - either they overcame the code-locks themselves or curious sentient species, not knowing what they were interfering with or influenced by the whispers from the imprisoned Serpents, unlocked the digital prisons.
By the end of the Great Crusade, one of the Serpents had been destroyed and another wrested from loyalty to Mag'ladroth. In early M42, the remaining five became known as the Five Fingers of the Hand of the Dragon and were in danger of freeing themselves and waking Mag'ladroth.
Inspired by Verity, Inquisitor Danforth Laertes, his entourage & allies including the Daughters of Verity undertook the Ophidian Crusade to defeat the Serpents, keep them imprisoned and prevent the waking of Mag'ladroth.
In order of chronological discovery by humanity, the Serpents are;

• Asirnoth the Great Silver Wyrm: defeated and destroyed by Ferrus Manus, Primarch of the Iron Hands Astartes
• The Seraph: freed by deceived Tech-Priests on Ophelia VII and imprisoned again by Verity
• Coatl: freed from the Wormspoil Hive on Necromunda by the Drake Union of House Goliath and fettered again by Candor, the prophetic child of the Ladies of Coatlaxopeuh of House Escher
• Unknown: on a Adeptus Mechanicus Forgeworld
• Unknown: on an Eldar Maidenworld
• Unknown: encountered in deep space
• Jinlong: imprisoned in the Dark Cells beneath the Imperial Palace and guarded by the elite corps of the Shadowkeepers known as the Hunting Lions, the "Golden Dragon" broke free and threatened the Throne and God-Emperor. It was only stopped by the sacrifice of Alicia and Danforth Laertes

Lifespan

Functionally immortal - on the order of millions if not billions of years