The Last Holdouts is received in Act 3 if Hawke supported Knight-Commander Meredith Stannard during the opening dialog and has made some effort towards the quest with the same name.
Letter[]
My men report that the blood mage hideout was cleared of all maleficarum. The Maker has blessed you with formidable strength, and it is fitting you use it to aid our righteous cause. We uncovered the location of their headquarters: a cave in Sundermount. Ser Agatha and I are gathering the faithful and will await you there.
—Ser Mettin