A maximum-level player requires exactly 176 Fragments of Power to learn every feat in the game. If you're farming Fragments of Power in The Unnamed City, you'll end up being quite familiar with the place. Assuming you kill all 7 bosses, you'll need to do 26 complete farming runs in the city to meet this cost. However, if you're using Legendary weapons or armor, you'll also gather repair kits for that gear, which is a great benefit to have.