Dragon Age 2 -
This is where the mage comes in handy. She will try and hypnotize Hawke. Interrogate her and let her go. Follow the arrow directly to the sanctuary. It is essentially a cellar in the southern portion of Darktown. Shades and Abominations will attack when you down the steps (if you have a rogue, there's a trap that can be disarmed as well). Run back up the stairs and use the chokepoint to your advantage.