White Dwarf #258 wrote:The loss of each and every Space Marine is recorded in Prospero's Lament, and although its veracity is in question, it remains the only account of the cyclopean Primarch's horrifying bargain.

"Magnus, squatting in his vast tower, watched in agony as his sons were torn to pieces by the barbarian Wolves of Russ. The howls of the pack resounded in his ears, destroying his concentration, breaking his psychic wards and driving him to the edge of madness. Bounding from his ebony throne, he flung his arms in the air and roared a plea for help, to save his Legion and their great works. As if something malign had been waiting for the Cyclops call, the sky grew dark and the air boiled with energy. Magnus was infused with eldritch power, his frame buckling as vile changes were wrought upon his body and his soul. He gazed out from the parapets of his citadel at the landscape of pain stretching before him, and screamed.

Hundreds of the Sons of Russ lost their minds completely as the magicks of Magnus took their toll. The skies cracked open, kaleidoscopic lightning blasting apart squad after squad of the savage Space Wolves. The very soil of Prospero sprouted ten-fingered hands like obscene fungi, clutching at the legs of the beast-warriors. And yet, they fought on regardless, sheer bloodlust inuring them against the numerous terrors now defending the citadels."

It can be presumed that this tale is continued from the Space Wolves' perspective of the titanic battle between Russ and Magnus, as related by the legend 'The War of the Giants', committed to memory by Inquisitor Bastalek Grim (1087345. M4I/5586741. P12).

"Magnus the Red took to the field of battle. The ravaged ground liquefying under his mighty strides As he cut a swathe through the ranks of the Space Wolves, Crushing everything in his path. Where his gaze fell, even the stoutest Long Fang turned white and died. The single orb in his forehead pulsed with an unnatural light. And his red mane stood on end with the energies coursing around him. Truly, this was an abomination in the eyes of the Emperor.

Leman Russ leapt from the thick of the melee to intercept the rampaging giant. As he turned, Russ grabbed one of the traitors by the throat and flung it at the giant's face. Magnus s petrifying gaze was blocked for a moment, and with celerity unheard of, Russ charged bodily into the crimson behemoth. And yet he did not fall.

The giant moved far faster than a being of such size might. Smashing his fist into Russ s chest with force enough to splinter his breastplate, pushing slivers of ccramite into Russs heart. But the Wolf-King was undaunted. Crabbing the giants arm as Magnus reared back for another blow, Russ was brought near to the giants face, and kicked him squarely in the eye. Magnus's roar of pain shattered the sky above, and thick black blood began to rain from the heavens.

Russ took his chance, and grabbed his blinded foe about the waist. Lifting the Cyclops clean off the ground, teeth grinding in a grimace of pain, The Wolf-King broke the Cyclops' back. The Thousand Sons, seeing their Primarch broken and cast down, turned and fled. But as Russ raised the Frostblade Mjalnar to deliver the killing blow. Magnus gasped a word of power and sank into the iridescent ground."

As for the conclusion of this epic battle, the accounts vary wildly. Some sources maintain that the sorcerers of the Thousand Sons opened a gate into the warp, fleeing into the jaws of Chaos rather than face the fury of the Space Wolves. Some claim that as his quarry escaped, Leman Russ swore an oath that he would destroy the legion to a man. Some claim that the traitor Legion became as ghosts, their diabolic patron protecting them from further harm.