Ailin Pasteur hails from Umoja. A skilled diplomat, Pasteur was "unflappable" most of the time. He is a wealthy man with receding gray hair which eventually faded to gray wisps with age, and a "weak" chin. Pasteur refused to drink alcohol, saying "there's no such thing as just one for me. Not anymore." Arcturus Mengsk had a complicated relationship with Pasteur, who at times admired him, mistrusted him, forgave him, and mistrusted him again.