Virgil Sanders is Thomas Sanders' fourth and long presumed to be final major Side. He was a former Dark Side before defecting. Virgil represents Thomas' anxiety, caution, vigilance, and his fight-or-flight reflex. His fellow Sides are Roman, Patton, and Logan.

Virgil is also the voice of reason, much like Logan, but does not attempt to solve the problems he sees in the same ways Logan does. He represents Thomas's fear, edginess, and overall dark nature. Virgil is a "self-deprecating emo" (implied by Roman and Virgil himself), and has gone through a lot of character development since his introduction.