Gatha was a researcher on Urza's Bloodline Project, who went rogue and continued his research in Keld. His researches were quite successful and he managed to make a keldon Witch-King Kreig so powerful that Kreig nearly killed a Phyrexian Inner-Circle monster when Phyrexians attacked Keld. Gatha died this day.
After his death, Urza collected his research results, and applied some in the creation of the metathran.
Many years later, his legacy lives on in the remaining Keldons known as Gathans.