Arden is first encountered at the Moonrise Towers Docks, where he oversees the departing cargo from his position at the very end of the docks. Interactions with Arden reveal that he aspires to be a True Soul.[1]
Should Acolyte Marls jump off into the water, Arden will react with complete confusion and shock. Further interactions with Arden will have him be nervous in front of the party, and attempt to be on the party's good side under the belief that Marls had disrespected a True Soul. He can then be told to fish Marls out of the water, to which he'd attempt to no avail;[2] doing so will have him move away from the Zhentarim Shipping Crate, allowing the party to interact or steal it.
Listening to Arden reveals that he doesn't actually care about Marls, and that he is attempting to salvage his armour, and not save the man himself.[3]
Defending Moonrise Towers
If the Nightsong is freed and the Harpers launch their assault on Moonrise Towers, Arden will be part of the remaining forces defending Moonrise Towers, and can be encountered in the ground floor hall standing behind Disciple Z'rell.
↑"And I don't plan on being a guard for long, True Soul."
↑Dialogue with the player: "I see. Then you'd better fish your man out of the lake." - Player "What? Beshaba's black bones - wait here. I'll find something to drag him out." "Not letting a decent suit of armour rot down there on my watch."
↑Dialogue to himself: "Least you could've done was strip off your gear first, fool." "I'd say a prayer for you, lad, but I honestly do not remember your name." "Must've found some booze among the supplies. Idiot."