Virgil represents Thomas's anxiety and caution. He 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. Virgil started out as an antagonist in the early episodes. His character arc parallels Thomas gradually becoming more comfortable with his anxiety. Virgil himself has stated that he puts on his dark persona as the best way to get anyone’s guard up. Although after said arc, Virgil has shown his more sensitive side, cooperating more with the other sides. Virgil has a notable pessimistic personality. His tendency is always to adopt the most negative interpretation, or to imagine the worst outcome of any situation. In some cases, this appears to be a confidence issue, and he is simply trying to avoid setting Thomas up for disappointment. Sometimes, Roman and Logan find his attitude a bit annoying, while Patton takes the opportunity to offer him encouragement. His negative outlook is also often employed for comedic purposes.
You got Virgil! Virgil is Thomas's Anxiety; his shame (or dare I say, paranoia). Virgil is an emo boy who honestly just needs love. He'll keep you on your toes with all of the possibilities he can come up with.