The Knights of the Nine quest line is significantly large and has been broken down into individual quests. Note that quests Nature's Fury through Stendarr's Mercy don't need to be finished in a specific order, however Nature's Fury must be completed before attempting The Path of the Righteous.
This quest begins when the Hero first hear of the attack at the Anvil Chapel.
The Hero will receive this quest once they have found the body of Sir Amiel and read Sir Amiel's Journal. In this quest they locate the old Priory of the Nine, which was once the headquarters of the Knights of the Nine, and recover the Cuirass of the Crusader.
The Prize for this quest is the Mace of the Crusader, but the Hero will need the Boots of the Crusader before they can get the mace.
In this quest the Hero will recover the Gauntlets of the Crusader.
As the heading suggests, in this quest the Hero will recover the Sword of the Crusader.