Teferi entered the crisis carrying an old decision. During the first Phyrexian invasion he had protected Shiv and his homeland of Zhalfir by phasing them away from Dominaria. The act spared millions from the war, but it also isolated those lands and created wounds that later became part of the rift network.
When the danger returned, Teferi helped bring Shiv back. Repairing that breach cost him his planeswalker spark. The loss was not symbolic: it ended the vast reach and freedom that had defined his existence. He accepted it because the alternative was to leave the wound open and allow the crisis to grow.
Zhalfir was the part he could not save. Without his spark, Teferi lacked the power to repeat the repair, and his home remained displaced. The Mending therefore gave him both an achievement and a lifelong absence. Much later, his search for Zhalfir would become central to the final struggle against New Phyrexia.