File: 1330465497.jpg-(176 KB, 480x680, Sleeper Agent.full.jpg)
To all the people saying "wait, wut?" at that fic:
Karn was created by putting former Phyrexian newt/sleeper agent/traitor Xantcha's heartstone (read: soul/core) into a golem by Urza, so Phyrexians merely reverted Karn to his original form. Although Xantcha's original form was probably not the raven-haired young woman she appeared to be, but I understand that the author wanted to take some liberties.
And Karn got the Meekstone and Mightstone from Urza, who indeed died/became part of Karn when they were ripped out of his eyesockets, but that's because Urza was a mere human first, got turned into a planeswalker by the stones, outlived his lifespan by several millenia and was a fucking disembodied head at the time. With the loss of his spark, he stopped being a planeswalker, lost access to the magics sustaining him and reverted to a mere human, so he promptly expired.
Karn, being originally a golem with a Phyrexian heartstone as its core, never had any such fleshly limitations and would survive losing the M&M stones, although he'd probably lose his planeswalker nature since it was transferred from Urza with the stones.
The man who wrote that fic is a scholar and you should feel ashamed for not reaching his level.
Pic related, it's (probably) Xantcha.