Wilbur wanders between the front entrance and front desk of the House of Grief in the Lower City. He guards the Mapping Room with Mirie and Morann. If a party member interacts with him, he welcomes them into the House of Grief, promising their burdens will be lifted.
If Shadowheart rejected Shar in Act Two and interacts with him, Wilbur sneers that she is more wretched-looking than the rumours claimed, and that she will learn her fate as soon as she walks through the front doors.