I have to ask this question - why not a single comment?...
Chapter Thirteen: Lamentatio Martis
Vox-Record: The Wormwood, Flagship of Sanguinius
Titan is fallen. There is no resistance beyond the Belt.
Then, we make Mars suffer for its defiance. Is the Weapon ready?
The Daemoncant, or the Hammer?
Yes, the Daemoncant is ready for transmission.
We attack now, then!
Iron Warriors tactical squad, Siege of Terra
Salamanders fighting during the Martian dusk (inaccurate depiction; created M37)
From Historia Martis
...When Sanguinius unleashed the Daemoncant on Mars, all Hell broke loose on the planet. The Daemoncant was part meme-weapon, part logic-virus, and part direct invocation of the Powers of Chaos. The factories turned on their masters, as men tore each other apart in mad rages, tech-priests being consumed by their implants and transformed into ravening machine-monsters that haunt Mars to this day. Riots in the crowded Hives killed many, as everything that could go wrong in the grand system that was the Forge World went wrong. Fail-safes faltered, as seventy-five percent of the population died in the great slaughter. Then the Daemoncant destroyed itself, purging itself from all the systems it had infected. It had been intended as a mere warning shot, but still Kelbor Hal was defiant. All the remaining forces of the Forge World, the Salamanders Legion, the Titan Legions Mortis and Ignatum, the tech-guard, everything that could be mustered, prepared to bleed Sanguinius as much as they could.
The Prince of Oblierators, Gabriel Santar of the Iron Hands, made planetfall at Valles Marineris, leading a war-host of 1,000 Obliterators. The Legio Mortis Imperator Dies Irae
was destroyed at the canyon, torn between fending off the Iron Hands ships in orbit and defending itself from the Obliterator-host. With it gone, the Iron Hands landed en masse, led by their Primarch, Ferrus Manus. The living metal that had covered his hands was now extruding tendrils through his body, increasing his stamina beyond even his brother Primarchs. But even he was to meet stiff resistance. The Skitarii tech-guard defended the Magma City courageously - at the battle's climax, Adept Koriel Zeth released the magma - destroying the city - rather than see her life's work perverted. The Seventh Company of the Iron Hands, sent into the Noctis Labyrinthis, vanished after reporting the existence of a 'nameless terror' in the region - from that point on, the area was avoided by both sides.
At the defence of Olympus Mons, the engine Aquila Ignis
of the Legio Mortis single-handedly held off hordes of traitor soldiers and the Obliterator Host of Gabriel Santar, now increased to 2,000 members. But then something happened that had been inevitable from the moment the Daemoncant was transmitted. The seals on the Vaults of Moravec failed. The daemon-engines within had long festered in the darkness, their hatred growing day by lightless day. They burst from the shadows, killing all in their path, rampaging toward the Omnissiah's temple. But far, far worse was to come. The Lord of Change Ghargatuloth, one of Tzeentch's greatest servants, possessed the Aquila Ignis
, overpowering both the Princeps and Machine Spirit of the Imperator Titan. The Titan began to spray Warpfire, and turned its guns on its fellow engines, destroying them. The Iron Hands surged forward towards a breach in the walls of Kelbor Hal's fortress, only one figure standing before them.
The Primarch slew Iron Hand after Iron Hand, until Ferrus Manus came forth, climbing atop a heap of his Legion's dead. The battle was brief, Ferrus breaking Vulkan over his knee after ten minutes of struggle, then casting the body aside. The Salamanders had lost their Primarch. Then, in the throes of victory, the living metal, empowered by Chaos, consumed Ferrus, transforming him into a Daemon Prince, a monster made entirely out of Warp-power and Empyrean-touched living metal. Ferrus' first words as a Daemon were simple - 'Kill all in your path'
. And that the Iron Hands gladly did. The Salamanders retreated to their Battle-Barge, Hammer of Nocturne
, but many tech-priests were not so lucky. Kelbor Hal was slain in combat with three daemon-engines, buying time for the populace of Olympus Mons to seek refuge in the Temple of the Omnissiah. When the Iron Hands reached the Temple, they found a silvery barrier that resisted even the mightiest guns of Aquila Ignis
, and that none of their number could pass, not even the mightiest daemon engine, without being consumed in white flame. It was a sorcerous ward laid by Magnus on his way to Terra, and it ensured that the Temple, with its stores of STC data, remained undefiled for the remaining duration of the Heresy. The daemon-engines of the mad, long-deceased technomancer Moravec obeyed the will of Ferrus Manus, who kept only a token number of Iron Hands on Mars, for Sanguinius desired a greater prize.