Legend Wrapped In An Enigma - Lestallum
First Available: Chapter 15
Other Requirements: Complete Dreadful Legend
Location: Lestallum
Rewards: 12,000 EXP & Ziedrich
Legend Wrapped In An Enigma can be picked up from Randolph immediately after turning in Dreadful Legend. This quest takes another ten level jump in difficulty so make sure you're prepared before taking it on. Once you're ready you'll want to head far south of Lestallum to The Fallgrove in southeastern Duscae.
Just a tad bit south of The Fallgrove Parking Spot you'll find a campsite which you can wait at until nightfall. Since the tonberry knights we need to defeat only come out at night you'll probably need to wait here to speed time forward. When you're ready head south from this campsite to The Tomb of the Tall, a Royal Tomb to the south. The tonberry knights spawn just outfront.
It's recommended that you bring some restorative consumables with you since the tonberry knights are a tough fight. Most of the attacks from these little guys will one shot your team members, knocking them down and forcing you to use an Elixir or Potion of some kind on them to get them back up.