The Island of Dread
This quest is assigned when Into the darkness has been completed. However, you are free to enter Dreadfell at any time, regardless of which other zones you have explored. The quest merely serves as a guide.
It is unclear what the quest name "The Island of Dread" refers to, since Dreadfell is located on the southern shore of Maj'Eyal, not an island. Most likely the name stems from the time when Dreadfell was still Tol Falas.