Synopsis

The campaign on One-Five-Four Four is not going well for the Imperial forces, and especially not for Ferrus Manus, primarch of the Iron Hands Legiones Astartes, who is troubled not only by the existence of the weaknesses within, but by the hinderances without as well; the terrain and fluid savagery of the Eldar enemies are taking a toll on his battle-group and placing him behind schedule. Even the latest victory, a battle commanded by his determined First Captain, Gabriel Santar, does not satisfy him, and neither does the proving correct of the Iron Hands' creed; the flesh is weak, at least out in the desert and at least where the attached regiments of the Imperial Army are concerned. Not only is Manus concerned with being behind schedule, and losing face in front of his brothers Mortarion and Vulkan, but the possibility that Eldar witchcraft could be causing his Astartes to under-perform fills him with ire.
Confessing his unease to Santar, Manus reveals that he has had strange dreams of late. What he does not reveal is that the sooner he gets the campaign finished and off the world, the better he'll feel. Deciding to abandon the Army if they cannot keep up, Ferrus Manus leads his forces deeper into the desert. Bion Henricos, acting as a liason between the legion and the soldiery, communicates this intention to their colonel, feeling a surprising twinge of remorse as he does so.
Unbeknownst to Ferrus Manus, two Eldar discuss his fate; one decides to intervene, to make sure that Manus walks along the more positive of the two possible paths leading to his future. The other warns against it, telling him that "stone cannot bend, it can only break."
The Iron Hands arrive at a suspicious valley; Ferrus Manus feels that it is important somehow, but is loathe to investigate it without a scout unit, something his current legion force is lacking. Henricos suggests waiting for the Army units to catch up and using their scouts - thus reinvigorating them by making them feel valued - but is shot down by his superior officers. Unwilling to wait any longer and not interested in using weaker units, Manus orders the Iron Hands to descend into the valley. Not long after the bulk of them reach the valley floor, a mysterious darkness engulfs them, followed by wind, storm and ambush. Eldar warriors engage the disorientated Iron Hands at close quarters, deploying a weapon which over-rode their controls of their bionics, robbing those with bionic eyes of sight, and turning the weapons held in bionic hands against each other...or their owners. The Iron Hands assault force is saved by the actions of Bion Henricos' rearguard, who're able to pick off the Eldar witches causing the sorcerous attacks. The Eldar retreat, leaving the Iron Hands to recover from the virtues of their own creed being turned against them...and notice that Ferrus Manus is missing...
Manus finds himself in a cavern system, assaulted by various visions and other sensory perceptions of death; that of his legion, his colleagues and even his own. He also comes across metaphorical representations of his brothers, and is momentarily puzzled by the feelings of betrayal looking at the statue of Fulgrim engenders. Combined with all this, he feels pursued by a malignant, serpentine entity. Irritated by such witchery, he presses onwards in exploring the caverns.
Gabriel Santar details fifty Terminators to assist him in the search, and assigns legion command to Shadrak Meduson, who is to continue their mission. Meduson and the straggling Army units eventually locate the enemy node complex they've been seeking to destroy, while Santar's team discover signs that Ferrus Manus actually vanished. Realising that he has been taken and they cannot do anything to get him back, Santar and his fifty troops decide to link up with the main force. The main assault is stymied by an energy shield of some sort that keeps out firepower, with Eldar defenders managing to hold back the Space Marines themselves for some time. Santar arrives, and comes up with a plan.
In the cavernous depths, Ferrus Manus is finally attacked by the serpentine monster that has been trailing him, the giant silver wyrm proving a vicious and poisonous foe. Nearly slaying him several times, Ferrus Manus is distracted by deja vu and a vague feeling of prophecy concerning the words "Angel Exterminatus", which appear in his mind as if from nowhere. Inspired by a memory of his brother Vulkan, he eventually wounds the serpent enough so that it retreats. Elsewhere, the two Eldar responsible for Ferrus Manus' predicament lament their allowing of an aspect of the Primordial Annihilator to sneak into their domain when they kidnapped the primarch.
On the surface, Santar's planned combined-arms assault goes well at first, with the Iron Hands penetrating the shield...until the return of the witchery that afflicts their bionics forces them to retreat. Once again, Henricos suggests an unusual plan; detaching his only bionic - his symbolic iron hand - he volunteers to lead the Imperial Army forces into the breached shield, and eliminate the Eldar threat. Initially hostile to this plan, which goes against their credo, the Iron Hands senior officers eventually relent.
Ferrus Manus continues onward, eventually reaching a bizarre, decrepit throne room, complete with rotting corpse on a throne. Coiled around it is the serpent, a great wyrm that Manus has come to believe is the spirit of Asirnoth, the dread wyrm of Medusa Manus thought he had slain long before. Wrestling with it and calling it out, he is shocked when the serpent begins to shapeshift into a familiar form, and with a familiar voice tells him that it is not Asirnoth. Recovering from this latest trick, Ferrus Manus angrily slays the half-primarch, half-scaled serpent beast, before tearing the corpse-king from the throne and opening the doorway concealed behind it. Confronting his Eldar kidnappers, he brushes aside their claims to be warning him against a likely future, attacking them and demanding his release. In desperation, the Eldar grant his request.
Bion Henricos' force of non-augmented humans takes horrendous casualties, and he himself is wounded, but they strike a solid blow against the Eldar. Before they can be wiped out, Ferrus Manus suddenly appears in the midst of the battle, turning the tide. The arrival of Santar and reinforcements secures the day. In a show of respect, the surviving humans are inducted as the first members of the Iron Hands valued mortal auxiliary; the Chainveil. Adopted Sons of Medusa, their purppose is to stand as a living reminder that not all flesh is weak.
Ferrus Manus refuses to answer questions of his experience, claiming that nothing happened that matters. He leads his forces into the jungle, in response to a request from help from Vulkan. In another place entirely, the two Eldar rue their failure, but take solace in the fact that even if the Gorgon falls, there is another who will suit their purpose...

Setting

One-Five-Four Four - an Eldar-controlled world, the Iron Hands fight to pacify the desert regions. The story takes place after the Emperor's quitting of the Great Crusade.

Characters

Ferrus Manus - Primarch of the Iron Hands
Gabriel Santar - First Captain
Vaakal Desaaan - Captain, 9th Clan Company
Shadrak Meduson - Captain, 10th Clan Company
Bion Henricos - 7th Sergeant, 10th Clan Company
Erasmus Ruuman - Ironwrought, 13th Clan Company

http://wh40k.lexicanum.com/wiki/The_Primar...y)#.T6AaK7Np4gc