"Remember that our strength lies in commitment to tradition and to each other."
Every alienage has a hahren, an elder. It falls to the hahren to arrange marriages for those without family, to negotiate with the guards when there's trouble, and to act as a sort of mayor and surrogate uncle to the people of the alienage.
The title, like so many things, is a holdover from the time of Arlathan, for hahrens are not necessarily the oldest person in their community, or even all that old. Tradition gives the role to the oldest soul, the wisest, cleverest, and the most level-headed. Valendrian has been hahren of the Denerim Alienage since he was in his thirties.
After "Unrest in the Alienage" if The Warden is a city elf:
He was taken across the sea by Tevinter slavers. His whereabouts are now unknown.
He was nearly shipped to Tevinter by slavers, but was returned to the Alienage by The Warden.