Tobin is Draven's son and an archivist for the Hand of Sirius. Despite his flippant demeanour, he is a deeply spiritual man devoted more to the Sirius side of the Hand than his father.
His main area of research is the Vampire Kings and as such he is a useful source of exposition on both them and the Shadowfel in general.
At present, his principle concern is avoiding being forced into an arranged marriage by his mother and grandmother, who are keen to add another title to the Elstina family line. He has considered pretending to be gay, but Draven talked him out of it.
He is heavily implied to be Quill's backup character in case something happens to Draven.