What We Know About Ugin
Ugin was a spirit dragon planeswalker who died on Tarkir many years ago in a battle with Nicol Bolas. The most notable parts of this planeswalker’s legacy were the imprisonment of the Eldrazi on Zendikar and a related colorless spell, Ghostfire. Ugin’s body has been recently found by Sorin Markov after laying many years in the icy chasms of Tarkir.
“It strode through the clash of dragons, the fall of Ugin, and the rise of the khans.” -Witness of the Ages
In the story “How Many Eyes?" we saw Ugin appear from what the main character believed to be a temporal rift. In Planeswalker’s Guide to Tarkir, we are told that Sorin has not seen Ugin "for over a thousand years". If we assume that Ugin’s death occurred within 500 years of the time when Sorin last saw him, the proposed timeline would prove that Ugin was dead prior to the Mending .
What does this mean for the story? This very likely timeline would mean that Ugin was actually present in the time fracture seen by the story characters in “How Many Eyes”. If all of the stated conditions are true, it leaves the important question of what the changed Tarkir will look like upon the arrival of both planeswalkers.
On a final note, there are other chained possibilities. If the rift which contained Bolas’ spirit was connected to another Multiverse, he would have the knowledge of an exit plan in the event of planar collapse or a more preferable outcome for his spirit. Perhaps the time stream and Multiverse where Ugin was saved by Sarkhan…