"Different. Examining genetic strands. Queen of Blades was efficient, ancient zerg qualities. Minor terran influence."
- Abathur 'examines' Kerrigan
Abathur was created by the Overmind as a "brood of one", spun from many species.
By the Overmind's instruction he designed the Queen of Blades by wrapping her in a chrysalis, though not without injuring her in the process.
After the Overmind's death, Abathur became feral and purposeless. He wandered under Char, eating whatever tried to attack him. He was too strong for Zagara to take control of him, and said that until recovered by Kerrigan, he was a purposeless "beast".
After the Queen of Blades was de-infested, she found him again and he helped her by evolving her brood. While Kerrigan was out on missions, Abathur experimented on zerg and searched for worlds where he could derive strains from existing breeds. When readied, he showed these to Kerrigan through demonstrations, and evolved the appropriate strain chosen by her.