Board Thread:Questions and Answers/@comment-27014396-20190219115838/@comment-24667049-20190219153905

From what I remember, it's like an upgrade tree. For upgrades like Slicer, you have to have both Limber Limbs and Swordplayer upgraded, as well as the Medallion of Brogends item equipped. For upgrades like Bound by Word and Brofist, you can only upgrade them if the character listed is nearby.