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Today I decided in light of the wake of the dreaded Invasion, I would do a
Biographical essay upon the race that inspired the great war ravaging the
surface of Dominaria as well as the unsung heroes of the battle fields. 
That's right!  Strap on your Grafted Skullcap and prepare to Twiddle your
thumbs while you read about the Thran and Metathran!

Thran-
Untold millenniums  into the mystical past of the world of Magic: The
Gathering- even  before Urza and his infamous brother Mishra had been
conceived.an ancient race of beings called the Thran lived upon the plane of
Dominaria.worshipping artifacts and living in a nirvana of utter contentment
and pacifism.until at one point they vanished off the face of the multiverse
without a trace of their whereabouts.

The Thran culture itself thrived upon the worshipping and study of artifacts
and other random mechanical devices.  The Thran believed that it was place
in the fairness of balance that both machine and nature be integrally
entwined with one another. each one functioning as an independent yet able
to work together as one.  Actions always speak louder than words. and thus
the machines the Thran developed were proof of this- each one was capable of
working alone with still a profitable output, yet the amplitude of their
efficiency was augmented when they worked together to perform a single task.

However.the peaceful era of the Thran came to a crashing halt when one of
the Thran healers in their society, Yawgmoth, sent shock waves across the
technological utopia when he went rogue as a heretic preaching about the
idea that nature was to bow down to machines. the only true perfection of
form being a meld of bio-organic materials melded into a mechanical frame. 
For this he was outcast by the Thran with his followers to a dark plane.left
to plan and scheme about a diabolical plot to return to Dominaria and
eradicate it's residents to remake it as he saw fit.

The Thran themselves disappeared off the face of Dominaria soon afterward,
and they would have remained a forgotten culture on the plane's ragged
surface if it were not for Urza Planeswalker who soon discovered the merits
of the technology the lost society left behind, adapting it to his own
accord in his efforts to wage war against his brother.

Metathran-
A gestation period of a few months.  Fighting instincts borne into every
cell in their body.  An impenetrable shield of loyalty and honor.

Shut yo mouth!
I'm just talking about the Metathran!
We can dig it!

When Urza found the remnants of ancient Thran technology. he began wondering
who these amazing people were, and how they were able to build such amazing
machines such as the Mana Rig in Shiv that were capable of creating so much
power with so little effort.  Urza soon began delving into the background of
  the mysterious race.  He soon found that although it was impossible to be
able to actually learn from a living specimen of Thran outside of Yawgmoth (
Good luck! ) , he soon realized that he could do the next best thing.

By using the ancient technology of the Thran assimilated into the technology
of the current Magic era, Urza was capable of cloning the Thran race into a
sub-species known as the Metathran.  The Metathran themselves are knock off
copies off the Thran, aside from a few almost unnoticeable differences.  The
one thing that sets them apart from what the Thran once were was the way and
for what purpose Urza concieved them for.

When Urza had found he had access to the DNA structure remnants of Thran
tissue, he knew that it would not only serve him well to revive this once
vibrant culture for study and social revamping, but also he could make a
cheap army that were loyal and hardy so he would be able to combat the
lurking Phyrexian army.  Soon he set off designing an incubator to house the
developing embryonic Metathran- by utilizing both his own and Thran
technological remains his design was complete and he began creating
thousands upon thousands Metathran soldiers.more or less regarding them less
than any sort of sentient and more of the products of an assembly line. 
Their worth was finally proved when the combat began against Phyrexia began.
  Although they were much smaller and weaker than their enemies, the
Metathran's "Never Die" spirit and superior numbers allowed them to take
short care of the scutas in a savage battle.  However, even with their
spirit, the Metathran were decimated and disintegrated by the dark Crosis
upon his rampage across Dominaria.