Kelder is involved in the quest, Magistrate's Orders.
Magistrate Vanard asks Hawke to look for a dangerous criminal who escaped and now is hiding in a Ruined Passage beneath some Abandoned Ruins on the Wounded Coast. Vanard already sent some members of the Kirkwall City Guard there, but they were slaughtered by unspecified "creatures". Vanard offers Hawke a promise of future support for the return of the criminal, as long as he is brought back alive and unharmed.The criminal turns out to be Kelder, Magistrate Vanard's son. You can choose to return him to Vanard, which will result in a 1reward (2 if you choose to blackmail Vanard), and rivalry from your companions, or kill him. Killing him will result in a reward of 1 from Elren at the entrance, approval from some companions, and a promise of revenge from the magistrate.