Colonel Aetos is a Venin. He was responsible for placing the lures and sending Xaden and Violet's squad there during War Games(Fourth Wing). Lilith Sorrengail also mentioned that she could've stopped Liam's death if only she'd paid more attention to what her own aide was doing.(Iron Flame, Battle for Basgiath, Page 612). He then sent Violet's squad to Samara, where she met Theopanie. It's specified that she realized that it was a trap, which leads back to Aetos who sent them.(Onyx Storm, Chapters 8-10)