This quest is available once you build the Hidden Ones Bureau in Ravensthorpe.
Speak to Hytham
After building the Hidden Ones Bureau, speak to Hytham and then follow him down to the docks as he explains a bit more about The Order and The Hidden Ones. When you get to the dock, use the small rowing boat to get across the river, then continue along up the path until you reach the top of the hill.
When you reach the edge of the cliff atop the hill, Hytham will perform a Leap of Faith down into a pile of hay. You will then need to perform the same jump. After completing your first leap of faith, follow Hytham back to the Hidden Ones’ Bureau. Upon finishing this quest, you’ll unlock access to a new page in your menu called Order, which shows you all of the Order Members that you’ll need to assassinate in this game. At this stage, a majority of the Order Members will be locked as you don’t have any clues on them. Order Members can either be only killed during main story quests or they are found in various locations across the world.
For most of the Order Members found outside the main story quest, you’ll need to find 1-3 clues to pinpoint their location, however, you can also just find them randomly when raiding or exploring - that’s not nearly as fun as playing detective though!
Upon completing this quest, you’ll unlock a clue for the whereabouts of Leofgifu the Scabbard and Hunta the Baldric. You will be given their exact location, so no need to find anymore clues to locate these Order Members!