His most visible function is to provide costumes and masks for forgetful partygoers during the Spring and Autumn balls, which require a masquerade mask or a costume. (Members lacking costume ideas can post in the cloakroom page asking Wilbur for an outfit. Another member will jump in as Wilbur and provide one.)
He also spends some of his time clearing out wyverns that roost in the porch rafters.
Wilbur is a dark blond, greying a little, and has golden-brown eyes. He may or may not wear half-moon spectacles; given his occupation, these could well be a prop.