Who is this "Zaunite alchemist" in Darius and Riven's stories?

In Blood of Noxus there's mention of a Zaunite alchemist responsible for the aftermath of a chemical attack.

"As this new war dragged on, it became clear that Ionia would not kneel. Riven’s unit was assigned to escort another warband making its way through the embattled province of Navori. The warband’s leader, Emystan, had employed a Zaunite alchymist, eager to test a new kind of weapon. Across countless campaigns, Riven would gladly have given her life for Noxus, but now she saw something awry in these other soldiers—something that made her deeply uncomfortable."

That's from Riven's new biography too.