During the time of Urza's bloodlines experiments on Tolaria, Gatha abandoned the project and began his own experiments in Keld. While originally seen as weak and unwanted, Gatha gained the support of the mighty Doyen Kreyohl and was thus able to carry out his work. Gatha's genetic tampering enhanced the Keldons into nightmarish warriors and culminated in the rise of the great Witch-kings, the mightiest of which was Kreig. Under the direction of Gatha, Kreig had Gatha made a Keldon Doyen thus giving him direct say in Keldon government. Many Keldons had long been insulted by the presence of Gatha and now saw this as a final straw. Led by the Doyen Varden, these Keldons rebelled against Kreig but were easily defeated. Soon, another threat would arise of Gatha and Kreig's rule of Keld. The Phyrexians had taken notice of Gatha's experiments and invaded Keld led by the inner circle member Croag. The Keldons began to lose the battle. Gatha, sensing the grave danger he had put Urza's bloodlines project in, cast himself off a cliff to keep his knowledge from the Phyrexians.
Kreig, inspired by his friend's sacrifice, charged Croag and gravely injured the Phyrexian demon before finally casting himself off the same cliff in defiance of his enemy. With Croag near-death, the Keldons won the battle but at a great price. The loss of Gatha and Kreig left a great power vacuum in Keld. The true-blooded Keldons regained control of the Doyen Council and made war on the Gathans, which ultimately led to their destruction. Many years later, Gatha's experiments resurfaced during the Time Spiral crisis. These Keldons were called Gathans.