Dyfed

Dyfed was the Thran planeswalker who showed Yawgmoth Phyrexia for the first time. She appeared as a young, strong, slender woman, with eyes that gleamed like crystals and skin like polished ebony. She usually wore tight black leggings with snake motifs, an embroidered vest with inlays of ivory, a silken scarf, and had beads braided into her hair.

Aiding Yawgmoth
One day, five millennia before the Brothers' War, Dyfed visited Glacian, the master artificer of the Thran Empire, wanting to meet in real life the genius who had proven the existence of the Multiverse by demonstrating its mathematical necessity, aware of his latent planeswalker nature. Yawgmoth, then the most important healer of the empire, walked in on the meeting and, after finding out the powers of Dyfed, managed to talk the planeswalker into aiding him. Dyfed fell to the charming words of Yawgmoth, and agreed to find a plane where Yawgmoth could build his own paradise for all the Thran. She even gifted the man with a special amulet, to call on her for help.

Creating the portal to Phyrexia
However, after Yawgmoth forcibly took control of the Thran Empire, Rebbec and Glacian summoned Dyfed, hoping to convince her to rescue the elders of the empire, whom Yawgmoth had imprisoned. Dyfed agreed to help Glacian, and took the elders, along with a number of goblin servants, to the plane of Mercadia, where they would become the ancestors of the Mercadians and the Kyren. Sometime later, as Yawgmoth amassed more and more power, but also drove the empire to war with the people of nations he had harmed in the past, Dyfed opened a permanent portal from Dominaria to Phyrexia, the metal plane which Yawgmoth wanted to make his paradise. Thanks to Dyfed, Yawgmoth could enter the core of Phyrexia, fusing himself with the plane and becoming its god.

Death
During the Thran Civil War, however, Dyfed planeswalked to Phyrexia, with the intention of putting an end to Yawgmoth's plans. There she met with Yawgmoth, accusing him of having spread lies about the phthisis, using the illness as a way to eliminate his enemies, and regretting the help she had given him. Dyfed ordered Yawgmoth to step down from his position, surrender to the Thran Alliance and free their delegates: Dyfed would then cure them of everything, short of phthisis. Yawgmoth at first seemed to yield to Dyfed and agreed to free the delegates. However, when the ruler of Phyrexia showed Dyfed the terrible experiments he had used the delegates for, she was utterly shocked. Yawgmoth, taking advantage of Dyfed's horror, stabbed her in the skull with a powerstone blade that scrambled her brain, preventing her from forming a coherent thought and, consequently, from planeswalking away. Thus Yawgmoth had his minions vivisect her, hoping to find an organ that allowed for planeswalking and have it transplanted into himself. However, before any such organ could be discovered, Rebbec found the tortured planeswalker and killed the priests working on her, allowing Dyfed to finally die.

Planes visited

 * Dominaria
 * Mercadia
 * Phyrexia
 * Pyrulea