During the events of the Fifth Blight, Dulin is already serving Lord Harrowmont for three years and seeks to protect him from Bhelen Aeducan's machinations, so the Warden must prove themselves before he will allow them to see Harrowmont.
Dragon Age: Origins
Dulin must be conversed in order to start A Lord's Trust: The First Task. If the Warden is of Dwarf Noble Origin and in the origin story ended the Warden successfully persuaded Harrowmont that Bhelen framed them, Dulin will remain unconvinced stating that the Warden and Bhelen previously allied to remove a rival and thus they need to prove their loyalty.King of Orzammar and the Warden makes the Ultimate Sacrifice, Dulin is seen at the latter's funeral, likely as the royal representative.
Dragon Age: Inquisition
If Harrowmont was made King, Dulin Forender will continue to serve as his second by 9:41 Dragon.Ordel of the miner caste will attempt to contact him about the unnatural earthquakes occurring in the Storm Coast demanding immediate assistance citing the fact that lyrium mines are critical for Orzammar's economy. However the letter is not sent and is found next to a corpse.