Quest 666

Walkthrough
The Demon Swordsman Proof increases the rate at which the Wave gauge fills up.
 * Talk to Agatha to start the quest.
 * We gotta find Diesel before all that bad stuff happens and he starts unleashing the D̷̮̦̺̘͓̐̇̃̇Ä̵̪̣́͗̐R̵̰̱͌͌̒K̷̨̞̖͂Ń̴͕̐Ĕ̴̩̙̪̯̻͗̑̔̕S̶̝̞̯̍̂S̸̡͈̍̉ on everyone and everything!
 * There's no telling where he is, so let's ask Villa and see if she knows anything.
 * Hightail it to T. Melsandy and talk to the bread connoisseur, Villa.
 * She needs a pick-me-up from Donk.
 * Yeah if I knew someone's name was D̵̛̬̻̽͐̏̊ǫ̶̮͙̜̦͌ň̴̢͓͉́̏̌͠ḱ̶̡̂̾̐̚, i'd cheer up, too.
 * Turn around and exit the Tavern. Right outside, in the garden, there D̷̡̗͋͐̏ǒ̴̜̙͝ṉ̷̔k̵̘̉̀̐ stands.
 * He makes vegetables cocktails... we've come into possession of a garlic-based energy drink.
 * Give it over to Villa and she'll energetically hone in on Diesel's location.
 * He's in Defel Wilderness, near the pyramids. Zoom on over there and find him in the aptly named tomb, "Tomb".
 * Prepare for a boss fight, then touch the tomb.
 * Enjoy the event.
 * Try not to cry.
 * Demon Swordsmen don't cry.
 * C̶̘͊r̸̻̽y̷̰̔ a lot
 * Head back to Agatha to obtain your Demon Swordsman Proof and complete the questchain.