This is a rift event. Once you reach the top of the keep and Alsbeth has appeared and said her part to the Hag, the Hag will open a Death Rift and call Werewolves to assist her. You will have 2 aves, then the Hag, to kill.
After, Laria appears and reveals that the Hag was her sister. Then a Messenger of the Vigil appears and tells Laria that the defense of the forest is no longer her task, that she has earned her rest. Then the Messenger will give you the choice to be sent back to Tearfall Run or stay and continue your other tasks.