Yes, Necrons can have fluff too!
Now into the thing:
The Host of Mehi-K'Amen
Whispers in the dark
In the old days when the Necrontyr where about to become the Necrons there was a mighty lord known as K'Amenhot re-a'-khetnebneb. His life was dedicated to the battle against the old ones, and his children where all Imer-esha, generals of the Necrontyr army. Under his command many worlds where taken. The ability of K'Amenhot to win battles was closely tied to his ability to receive visions from the Messenger, as was the Deceiver known in that era. The lord of war, as was K'Amenhot known by other races, would always know beforehand if his troops would be victorious or not, and thus he could choose when to commit to battle and when to plot a new strategy.
But a single successful Imer-eshaneb was not enough to turn the tide of the war, and by the plotting of the Deceiver the Necrontyr where doomed to failure so that they would embrace the metal curse their gods would cast on them. But to the cunning c'tan K'Amenhot had to trust his visions and auguries, and so every one of them led to victory. The messenger would visit K'Amenhot more and more often, and his victories would come one after the other in a manner that he questioned these omens no more, relying purely on the c'tan words to shape every step on his way. In a way, this was the doom of all Necrontyr.
It was not surprising then the day when K'Amenhot recalled all of his host to an empty giant moon in a distant system at the brink of the galaxy. His visions had taken a hold of him, and the messenger urged him to build a machine. The workings of this device or it's purpose where still a mystery to the lord or any of his followers, but they relentlessly spend every resource they had in it's making.
When the device was completed, it's workings still shrouded in mystery, was when the c'tan unveiled their plans for the entire Necrontyr race: To give up their flesh in trade for deathless, eternal life. Since the start of the making of the device that the voice and visions of the Messenger had ceased. K'Amenhot himself was drained by the effort put into this last task. He was unsure if his work was discarded by the c'tan, capricious as they where, of if it was to be kept secret, for use in a future moment. His life was at an end, and all his past victories where of no value compared to his entire race defeat in war.
It was also at this moment that his youngest child came to life. Nefretreswet was it's given name, a beautiful dream. K'Amenhot was torn in two as his desire to turn the tides of war and embrace the deathless form of the Necron would take his daughter away from him. It was in the midst of these heavy thoughts that a whisper from the deceiver sparkled into his mind. The device he had built was an ark to preserve the life of a single Necrontyr for millenia, as well as preserving the memories and will of himself and his host.
K'Amenhot and his host where on the Necrontyr home world at this point, and he knew that other Necrontyr would sought to siege the control of the device from him. As the rituals to give away all flesh to the living metal of the c'tan where recited his entire fleet was hurrying the void back to the moon where the device was built. The Deceiver also knew that the other c'tan would not see trough the many layers of his plot, and helped K'Amenhot keep these machinations secret. When they arrived at the device, K'Amenhot rushed with his child at his arms to the center of the machine, and placed her frail body inside the core. As if already expecting it's contents, the whole device started to function and came to life. The energy released from it's workings killed all the Necrontyr in the moon and transferred their minds to the metal bodies of Necron hidden deep in the moon.
The Necrons came to be in that moment. But the boon was also a curse, and this transformation was the end of the Necrontyr as accounted by all of the other races records. But the c'tan are capricious and cunning beings, the Deceiver the most. And trough K'Amenhot he prepared yet another betrayal, and started off another curse. Hidden in this distant moon was another masterpiece of lies.
The deceiver's deceit
Since the c'tan have tasted the energies brought by war and suffering from the living they have foregone their former immaterial forms to manifest in the physical world. Since then they have tasted different kinds and perfected their taste to the many different spectrum of a life's end: Pain, suffering, terror, desperation, insanity... Each has it's own twists and flavors that they relinquish in. But the Deceiver, off all remaining c'tan, has the most accurate taste. One of his works, the machine built by the former Necrontyr K'Amenhot, one of the foulest and most vile of these delights: The life energy of the unborn.
Just as the Necrons are a cursed form for the Necrontyr, the machine that was promised to keep the life of Nefretreswet also had a twisted purpose. Instead of preserving what would become a living being, the machine constantly harms and tortures the cells of a the young body in development so that it never ages, but never heals. In this constant state of growing and dieing at the same pace the body of Nefretreswet is kept artificially ever alive. Her spirit, in the other hand, having never known anything but the ever constant pain was shattered beyond any horror the warp could spawn. This tortured soul is prey to the Deceiver's will, a rare taste that only his mind could conjure and manifest. The last living Necrontyr is but a withered and suffering ever-living mass of life inside a device forgotten in a distant moon.
But the Deceiver works on layers upon layers of schemes, and as the Necron entered their millenia long slumber the messenger returned to what once was K'Amenhot re-a'-khetnebneb, undefeated lord of battle from the Necrontyr, and instilled new images and visions of greatness for he and his followers. The former K'Amenhot, now known as Mehi-K'Amen, and his entire army where different than the rest of the Necron legion. Their task was not to wait in slumber, but to care for the device they had built and keep it safe and working. Thus, in the distant giant moon at the fringe of the galaxy, the Necron stayed awake.
All the Necron that where created by the Deceiver upon activation of the device where different. Their bodies where made the same as every other Necron, but their minds where captured by the device to fuel their watch over it. Different from the rest of the Necron, these preserved a much greater degree of their former intelligence, but their spirits where forever lost. These shards of personality manifested in Mehi-K'Amen, and as Necron Lord over these deathless watchers gave birth to the Host of Mehi-K'Amen.
The Host did more in their millenia servitude as keepers of the Deceiver's device. The shards of Mehi-K'Amen personality made him seek a way of allowing his former daughter to grow again, free of the device that kept her body ever-living in pain. The Host of Mehi-K'Amen made experiments on cloning and life-supporting for millenia and perfected this technology. But what they could not understand they could not dominate, and thus every cloned Nefretreswet shared the same shattered, suffering spirit of the original. Finding himself unable to execute even the clones of his daughter, Mehi-K'Amen sought a way to make them useful in battle.
Clad in a life supporting chamber with the same technology as the original device, these clones are ever-living tortured and frail bodies. Linked to their mind are powerful tentacled arms with gauss-flayers and sharp blades. When deployed in the field they seek to end their suffering by inflicting pain and death upon their enemies. Thus the Deceiver's plot unfolds into yet another twisted creation. They are called the Mourner.
The Host of Mehi-K'Amen units:
Since they remained with their minds in a much more preserved manner than the rest of the Necron, the Host of Mehi-K'Amen necrons preserve their humanoid forms as much as possible. The main difference to be noted is in the Wraiths and Destroyers, where the parts that support their roles in battle are made like light vehicles or suits, rather than a different shape of body like expected. All of the Host's Necrons are able to talk and have more personality than usual Necrons. They often scream and curse in their ancient language as they fight their enemies.
The other mechanical elements of the army have been subject to improvements over the ancient designs, such as the Tomb-spider being redesigned as the Tomb-guardian, using tentacled and more versatile arms than their original design.
The last thing to notice is that they use Necrospheres instead of Monoliths. These vehicles resemble the Deceiver's device in appearance and use an improved power matrix in the form of the energy sphere inside of it, much more powerful than the crystal of a common Monolith.
Lastly, the Host of Mehi-K'Amen have not adopted the Pariah technology but focused on the creation of more and more Mourners, that fill a similar role in combat, but are much more powerful, with a single Mourners being equal to a squad of five to ten Pariahs.
Take a look at my Progress Log for the conversions here: http://warseer.com/forums/showthread.php?t=189052