Garth

Garth One-eye (Galin) was a powerful wizard. He was the son of Cullinarn, the master of the green-blue House of Oor-tael. The house was destroyed by Kuthuman, the vizier of Estark, who was on a quest to become a planeswalker. Garth was five years old at the time of the event that would be known as the Night of Fire, and Zarel gouged his eye out to torment his father. Garth ran back into the burning House and Zarel believed he was dead. After twenty years in exile, Garth returned to Estark and manipulated the remaining houses and the new vizier so that he could win the tournament and meet Kuthuman. He was successful, ascending and defeating Kuthuman. He willingly gave up his powers to live with the Benalish woman, Noreen, he met during his adventure.

Later he would break his pledge to never use magic again when he met Greensleeves.

On Garth's Spark

Garth appeared only in prerevisionist books, in which there was no mention of a planeswalker's spark: any mage could break the plane's veil with the right spells and sufficient mana and travel across the planes. To make the prerevisionist books fit Revisionist Continuity, many people believe that wizards who became planeswalkers by spells actually possessed sparks that were flared by the spells they cast, but didn't know of these sparks or their role in becoming planeswalkers. However, Garth might be an exception to this theory. The novel Arena states that the spell researched by Kirlen could grant the powers similar to those of planeswalkers to anyone casting it. Its not likely though, that Kirlen created a real spark with her spell, because even planeswalkers don't understand its nature fully. So the explanation of this fact might be that the spell just simulated powers of spark in some extent.

On Garth's Mana

Green mana: summoned a war mammoth, become mist. Conversely, didn't have regeneration to fix his eye.

White mana: healing

Red mana: Fireball