William Kreisler was a scientist specializing in botanical research. Limited information exists for his previous careers, but he was a known employee of the KemSynth corporation and a participant of tests on Project Dark Mirror, a means to develop nerve gas using flowers from South America.
KemSynth supplied Kreisler with a laboratory adjacent to an oil facility owned by the company's Petroleum division. Kreisler, operating within Security Section D, cultivated the plants harvested from Peru. When Red Section invaded the Alaskan oil site to obtain Dark Mirror, its soldiers captured Kreisler for information on the project.
Gabriel Logan and Lian Xing were on site for a Precision Strike operation when they learned of Kreisler's identity. Intercepting Red Section radio traffic, Teresa Lipan warned Gabe that Black King, the onsite commander, considered the scientist expendable and a soldier left him to suffocate to death in a gas chamber. Gabe succeeded in stopping Kreisler's asphyxiation, but the civilian committed suicide using one of the plants instead of surrendering the KemSynth project to Logan.