I found Garren's Daughter!
  • 1 of 6: Talk to Garren's daughter.  She tells you that letting her out would be sufficient.
  • 2 of 6: She says the key is on a wizard.
  • 3 of 6: So go into the cavern entrance, go down, and talk to the real Firkraag, an ancient red dragon (they had to stick one in eventually, didn't they?).
  • 4 of 6: He tells you he is bored of you and will let you go and that you can fight the wizard for the key.
  • 5 of 6: Tell him you will fight the wizard first.  The wizard Dimension Doors upstairs.  Go up and destroy him.  True Sight helps, but he's really only a minor nuisance.
  • 6 of 6: Go back to Garren's cabin to complete the quest.