Chief Custodian Captain General Aecar Arshenzo leads five hundred Custodians through the Imperial Palace toward the Senatorum Imperialis. Never in his nearly one thousand years of life and service to the Emperor has he received a message that chilled him to his core like the one he received from his men assigned to the Sanctum Imperialis. An intruder had appeared at the foot of the Golden Throne, mere feet from the Emperor of Mankind. When engaged by two of the Three Hundred Companions, the most elite warriors of the Custodian Guard. The intruder simply shut down their power armor, somehow leaving them face down and helpless before the throne as he disappeared. But not before uttering words that would forever echo in the mind of every Custodian who heard them.
"Just about as useful as him."
He had insulted not only the Emperor but the entire lineage of the Ten Thousand. Aecar would see that stain removed. He had called for the entire Palace to be put into lockdown and for every member of the Ten Thousand patrolling it to go on alert status Ultax, which is the status below Terminus, which is reserved for an invasion of Terra. Under Ultax, the Custodians will detain, engage, or eliminate anyone they find suspect without care for their rank or status. This is why everyone in the Palace knows to remain in their assigned or current areas to obey all commands given and answer all questions asked. When word was sent out, all areas of the Palace replied in the affirmative except for the Senatorum Imperialis. The reason for this soon became clear when all signals from that area of the Palace went dark. No, answers on the vox and no visuals from the security pict recorders.
Further scans of it found no signs of life within that entire section of the Palace. No Custodians, High Lords, or anyone else. They had all disappeared. What was found was incredible levels of energy, which the most powerful logic engines in the Imperium could not begin to classify. All one member of the Mechanicus could tell him was that it resembled the energy of pure creation. Not the creation found within a forge but the creation of a star. How such a thing was possible on the surface of a planet, let alone in one space of the Palace without tearing both apart, none of the priests of Mars could tell Aecar, though, by that time, they had started heatedly talking in machine code to one another over the data that was coming in to care about much else.
Normally, so huge a force of the Emperor's guardians would be enough to prosecute any action up to and including the subjection of entire star systems. But Aecur had called in five hundred more of his brothers to converge on the Senatorum Imperialis from the opposite direction. There are few forces in the galaxy, indeed, that can stand up to such a force. As his five hundred reach the first Hall of the Senatorum Imperialis, they all come to a shocked halt.
Custodians are trained to fight any enemy of the Emperor. Their knowledge of such things goes deeper than even that of the Inquisition because their libraries are the Emperor's libraries. They are aware of enemies, both present-day and forgotten due to the passing of time. Standing before them are eight-and-a-half-foot-tall, humanoid beings of pure featureless silver. They stand in perfect ranks that fill the hall. The closest things that Aecur could compare them to are the ancient thinking machines known as the Men of Iron. Creations of humanity's ancient past during the Age of Technology that almost brought the race to extinction. But these things look only passingly like the ancient sketches and picts.
"Captain General," says Jerac Dolio, "What are your commands?"
Aecur experiences another first; he doesn't know what to do. Before he can give a command, the silver giants start to disappear row by row. There is no teleportation flare, but he knows they are teleporting. How he doesn't know because none of the Custodian's attempts worked, which is why they came on foot, but that doesn't matter as much as where they are going.
"All stations, all stations," yells Aecur into his helmet vox, "This is Captain General Aecar Arshenzo. Terminus, I repeat, Terminus. An unknown force of silver colossi has invaded the Palace. They are almost certainly machine in nature and are using advanced teleportation. All forces engage on sight. Custodians charge and fire!"
He and his brothers move as one like a golden tide charging forward with Guardian Spears lowered and firing, attempting to catch the next rank of silver giants before they disappear. They miss but catch the ones behind. Their bolts hit, but to their shock, the giants don't stagger or take a single step back. The Custodians switch tactics as one powering on their spear blades' disruptor fields. Aecur and two others all strike at one. Aecur goes for the decapitation, only for the thing's hand to move up in a blur, catching the blade of his spear. The powered blade cuts into the hand but barely, and Aecur can't move it an inch, even with all his transhuman strength. The other two strike at its torso and leg with much the same result. Their spear-bladed cut and stick. All around them, the scene is repeated. The Custodian tide crashed against an unmoving silver rock face. Then, the machines attack.
Moving faster than even the Custodians, the silver giants attack with metal limbs. Aecur is yanked forward by his spear before a metal fist slams into his faceplate. His vision darkens as he is thrown back, landing hard on the marble floor. He gets up quicker than any mortal could have; any regular man would not have a head but still far slower than normal. That blow was like getting hit with a warhammer wielded by a Space Marine. His helmet is damaged and dead. He reaches up and pulls it off. The sounds of chaos around him rush back.
All around him, his brothers are being taken apart by the silver giants. They are being disarmed, and the giants are beating them barehanded. Custodians are sent flying with buckled and broken auramite armor. Aecur watches as the Guardian Spears stabbed into or taken by the silver giants are absorbed into the liquid-like metal. The giants move forward, beating down any Custodian who continues to try to fight or who gets up off the floor. Aecur realizes they are not killing them. They are literally beating them to the ground and keeping them there. Before Aecur can see more, another silver giant is on him. An armor-shattering, bone-breaking blow is driven into his chest. He flies back, slamming into the wall. His transhuman physiology is pushed to the very brink. Then, past it as another blow is driven into his gut, cracking the wall behind him. Aecur slumps forward into darkness.