Sister Tanner is a Chantry Lay-sister in Redcliffe Village.
Involvement
The Inquisitor can find a letter that reveals that Tanner is in fact a smuggler. They can choose to confront her about her about her Business Arrangements and if they possess the "Underworld Knowledge" perk, or if Cassandra, or Varric are present, she can be convinced to join The Inquisition as an agent working for Leliana. A History Knowledge reply is also available and appears to recruit Tanner, however she will not show up as an agent in the Perks listing at the War Table.