‘At last! Your true colours,’ said Fulgrim. ‘For all your talk of honour, you will not face me alone.’

Angered, he rained a flurry of blows down on Guilliman, driving the primarch back up one step, then two. The bolts aimed at the daemon primarch were turned aside by diabolical art, and he stood in the full face of the Ultramarines’ attack.

‘My sons are here to greet yours,’ he said. ‘Let them join the revel.’ Parrying Guilliman’s attacks with insolent ease, Fulgrim threw back his head. His jaws opened wide enough to swallow a man whole, and he let out a shrieking ululation.

From the far side of the Heliopolis, a harrowing, discordant noise answered the call of the daemon primarch. From the upper tiers of the Heliopolis’ seats marched the twisted warriors of the Emperor’s Children, many bearing sonic weapons from which came the thrumming of destructive music.

‘Now, we shall see whose children will survive!’ snarled Fulgrim, and came at his brother. Guilliman countered and parried, his mighty gauntlet batting aside Fulgrim’s swords as his own hunted through the cage of steel Fulgrim wove with his four blades, seeking out the tainted flesh behind.

Fulgrim snarled as the tip of Guilliman’s gladius nicked his skin. Rising up on his tail, he swept down with his swords in quick succession. Guilliman’s weapons found them all, turning them aside with economical movements. Nevertheless, he was sorely pressed. He had fought daemons of every kind on many worlds and bested them all. Fulgrim, however, was an unholy blend of primarch and daemon. In him, the energy of the warp was married to the wisdom of ancient sciences. He was part material god, part immaterial daemon lord, and his power was great.

Guilliman cut and feinted, using the Hand of Dominion to catch the sword wielded by Fulgrim’s lower-left arm. The unholy metal of the blade cut into the thick ceramite of the gauntlet, and corrosive poison spattered the Armour of Reason, eating into it with smoking ferocity.

Pain somehow afflicted Guilliman through his armour, as if his war-plate itself were hurt. A spicy agony burned up the nerves in his arm from his interface sockets. He gritted his teeth and twisted the gauntlet. Energy crackled and banged, and the sword snapped in two. Ichor pumped from its hollow innards. Strings of flesh tore free as Guilliman cast the broken tip aside. Fulgrim screamed as if his limb had been ripped off, and he recoiled. Guilliman fought against his own pain to slash hard with the Gladius Incandor, cutting deeply into Fulgrim’s swordless arm.