In order to complete the quest, this item is needed in the battle against Count Draynor, a Vampyre that became weakened from the ordeal of crossing the blessed River Salve to leave Morytania. He is even the brother of Lord Drakan. Being so weak, it doesn't require a Flail of ivandis to kill him; you only require a more classical stake and a stake hammer. The Morytania vampyres, presumably being much stronger than Count Draynor in his weakened state, require a more straightforward approach than a hammer and stake.