“We don't owe you any explanations for our actions. We have a sacred duty; failure to protect Her would be a greater sin. All will be forgiven.”
Eirik is the revered father of the Haven Chantry as well as a mage specializing in healing magic. A man is in charge of this chantry instead of a revered mother because Haven has been isolated from the rest of the world for centuries and never adapted to the reforms that the rest of the Andrastian Chantry went through.
This section contains spoilers for: Dragon Age: Origins.
Eirik was responsible for detaining Brother Genitivi. When the Warden enters the chantry to speak with him about the Brother and of what they have seen in the village, Eirik comments on how outsiders are not wanted in Haven, and attacks the party. After he is defeated, it is possible to open a secret door in the chantry to the room where Brother Genitivi is being held.