Storyline
With the skyship Weatherlight completed, Urza now works on a eugenics program to create a perfect crew for it, as well as engineering a race of soldiers to fight the Phyrexian invasion. One of his geneticists, Gatha, defects, and uses his knowledge to improve the Keldon race. Meanwhile, the Phyrexians create the plane of Rath as a staging ground for the invasion.
Read more about this topic: Urza's Destiny