Walkthrough
After eventually finding the Sticky Honey with Hop, return to the Master Dojo and talk with Mustard. He will be surprised that you found the secret ingredient since he didn't tell you what it was, so much so that he will challenge you to a final battle in order for you to become a Dojo Master. (Before you do, you can make the Max Soup you need in order for Urshifu to Gigantamax by heading to the Dojo Kitchen.) After defeating Mustard and his own Gigantamax Urshifu, you will be deemed a Dojo Master. This will conclude the Isle of Armor Story.
Dojo Master Mustard: Level 73 Mienshao, Level 73 Luxray, Level 75 Lycanroc, Level 74 Corviknight, Level 75 Kommo-o, Level 75 Urshifu
Now that you know about the final battle against Dojo Master Mustard, Click Here to learn how to challenge his wife, Honey, to a secret battle!