Badge of Vows 98 is a quest item from the From A Different Sky - Part 10 DLC. Merely picking it up satisfies the goal needed to complete the quest.
Badge of Vows #98 is located in Cutlass Cape in the Pastona Cavern, near the Bluemoon Tower. It is on top of a broken archway. To reach it you will need to levitate to the southern remains before leaping to the neighboring platform.