In a time soon to come, Karn will be liberated. The tendriled throne of Phyrexia will no longer bind the silver golem, nor will the plane itself. The shackles will fall, and he will know that his would-be servants were actually his captors.
But this new freedom will come at great cost. A mission of conscience will beckon him, guiding him to retrace his own tainted steps through the multiverse. He will bear the crushing grief of an entire world, with a splinter of knowledge lodged in his mind that a plane of his own creation has fallen to the very enemy he was created to help defeat.
The future will not be an easy path for him.
He was made to withstand the ravages of time, but correspondingly, his memories endure through time as well. He will set his mind to make things right, but he will carry with him the wrongs he has caused. He will learn that some wounds cannot be mended, and that some losses will never be reckoned, even if this enemy can be defeated one day. Hardest of all, he will be forced to admit his own role in Phyrexia's victory.
Soon, this future shall be upon him. And with it, from an unlikely source, a spark.
At the present moment, it is a time of Phyrexia's triumph. The silver golem Karn experiences flashes of lucidity while bound into the throne of the Father of Machines. In these moments, he grasps his whereabouts and his situation, and can utilize the full power of Phyrexia's reconnaissance to observe the state of the plane around him. He understands that he must free himself, somehow, from the yoke of Phyrexia, lest he lead them to their dark goal of conquest. But his faculties return just in time for him to see the bitter truth. They've already won.
Under the leadership of the Praetors, the Phyrexians advance across the metal-plated landscape. Exarchs and vat priests oversee the conversion of Mirrans into Phyrexians. Obliterators mercilessly shred all attempts at resistance. Birthing pods generate ever more grotesque Phyrexian life forms, and the former vestiges of Mirran civilizations are melted down in the deep furnaces.
Through his own eyes and with his own mind, Karn witnesses the conclusion of Phyrexia's triumph over Mirrodin. The Phyrexians roam at will now, spreading throughout every cranny of the plane, claiming it as their own. Those brave natives of the metal world, the Mirrans, are now a scattered handful of resistance fighters, seeking refuge like prey species.
Even for Karn, a metallic artifact creature crafted by Urza, it's too much. His mind cracks at the horrible irony, and the oil permeates his body. Unable to muster resistance, he yields to Phyrexian whispers. If no one intervenes, he truly will become the Father of Machines, betraying everything he stands for.
Not many who live can say they accomplished the exact task they were created for. Not many can claim they were able to realize their destiny. But many years ago, in one blinding moment, Karn realized his.
Karn stood at the epicenter of the Legacy. The storied artifacts were brought together from across many worlds, forming a weapon capable of a fateful act of destruction. Karn was the unifying principle, the lynchpin, the cauldron in which the reaction could take place. And when all was assembled and assimilated into him, he became the barrel of the cannon.
Yawgmoth, the Father of Machines, was obliterated. Dominaria was saved from the Phyrexian invasion.
In the act of Yawgmoth's defeat, Karn became a planeswalker, and the seed of future events was planted. Karn, the only artificial planeswalker, became capable not only of traveling from world to world, but of creating a world himself. He would go on to create a shining world of metal that he dubbed Argentum, later known as Mirrodin.
But Karn doomed his own creation. Karn himself was the germ of Phyrexia's growth on Mirrodin, inadvertently bringing the contagion to the plane. He left it to grow and spread, and when he returned, it was too late.
As Karn fell to his created world, all seemed lost. His planeswalker spark was gone—sacrificed to seal a massive rift in time. His mind was gone - finally succumbing to the power of the oil that lurked within him. His hope was gone - shredded by seeing his creation tainted by the growth of his sworn enemy.
Deep in the planar core, Phyrexians took Karn prisoner, and constructed for him a throne.