Fenn is the medic of the Strays. Seldom sugarcoats things. He studies all the infected alters they keep at headquarters and is in charge of taking care of them, though he's not...the best at that.
But y'know what he IS good at? Inventing the cure to the virus! His family and predecessor for generations had been living in the Zoo, researching for an antidote, and Fenn was the one to complete it.

He is a descendant of Octavia Fenn, a human from Old Earth who opposed the founding of the Bastion.