Mustard

Your first encounter with Mustard is when you first enter the Dojo. Honey introduces you as the last Dojo member, but Mustard insists on battling you to see how strong you are.

Dojo Master Mustard	Mienfoo	Shinx
Battle Type Items	Level 13	Level 13
	Attacks: Fake Out U-turn Force Palm	Attacks: Bite Spark
	Hold Item: No Item	Hold Item: No Item
Pre-Champion Cup

Dojo Master Mustard	Mienfoo	Shinx
Battle Type Items	Level 61	Level 61
	Attacks: Fake Out U-turn Force Palm	Attacks: Bite Spark
	Hold Item: No Item	Hold Item: No Item
Post-Game

Defeat him and he will give you the Dojo Uniform and tell about how there's only limited spaces in the dojo and how every student must compete for the Sacred Armor. However, when Klara/Avery ask for their uniform, three Slowpoke come in and steal it. Mustard tasks everyone with the task of chasing down the Slowpoke and retrieving the uniform. These are found in the Soothing Wetlands and have to be defeated.

When you have completed the task, you will return to Mustard and he will mention how you're the first since Leon to defeat all three Slowpoke on your own. The other students say it's unfair so he gives them another chance to do it.

Following that, the next trial is given by Mustard. It's time to make Max Soup and to do that, you need to find some Max Mushrooms. As you're not from the Isle of Armor, Mustard takes you to where they're found so that you can participate.

When you return having found the Max Mushrooms, Mustard will take you to the table to talk about how the Max Soup can help Pokémon be capable of Gigantamaxing. After that, he mentions that only you and Klara/Avery have got this far and so gives you one final trial, the need to battle one another.

Defeat Klara/Avery and Mustard will offer you his congratulations and give you the Secret Armor of the Master Dojo: the Legendary Pokémon Kubfu.

With Kubfu, he says you need to make it your Best Friend so suggersts going to multiple different spots to boost its friendship. When you return, he will mention about how you can evolve Kubfu by taking it through the Tower of Darkness or Tower of Waters and suggests you pick a tower and challenge it with Kubfu.

Regardless of which towerr you choose, Mustard will be the final trainer you face and will face you with a Kubfu himself.

Dojo Master Mustard	Kubfu
Battle Type Items	Level 30
	Attacks: Aerial Ace Focus Energy Brick Break
	Hold Item: No Item
Pre-Champion Cup

Dojo Master Mustard	Kubfu
Battle Type Items	Level 70
	Attacks: Aerial Ace Focus Energy Brick Break
	Hold Item: No Item
Post-Game

When you defeat him, he will suggest that you take Kubfu to the scroll to evolve it. If you use an Everstone on Kubfu he will suggest coming back when you do wish for it to evolve.

After you have become Champion and have evolved your Kubfu, the next part of the story with Mustard begins. When you enter the dojo, Hop will be there and discussing elements of his research with Mustard. Mustard will tell you that Urshifu is capable of Gigantamaxing. He will mention that regular Max Soup cannot work and that there's another ingredient needed for Urshifu to Gigantamax, but he has forgotten what it is. He tasks you and Hop with finding it.

After you have found the ingredient and made the Max Soup to Gigantamax Urshifu, Mustard will request a battle with you. He will use the Urshifu of the form different to yours which also Gigantamaxes

Dojo Master Mustard	Mienshao	Luxray	Lycanroc	Corviknight	Kommo-o	Urshifu
Battle Type Items	Level 73	Level 73	Level 75	Level 74	Level 75	Level 75
	Attacks: Fake Out U-turn Blaze Kick Close Combat	Attacks: Psychic Fangs Wild Charge Crunch Play Rough	Attacks: Accelerock Stealth Rock Stone Edge Play Rough	Attacks: Iron Head Brave Bird Body Press Light Screen	Attacks: Clanging Scales Aura Sphere Flash Cannon Clangorous Soul	Attacks: Surging Strikes Close Combat Poison Jab Iron Head
	Hold Item: No Item	Hold Item: No Item	Hold Item: No Item	Hold Item: No Item	Hold Item: No Item	Hold Item: No Item
						Gigantamax
Tower of Darkness Beaten

Dojo Master Mustard	Mienshao	Luxray	Lycanroc	Corviknight	Kommo-o	Urshifu
Battle Type Items	Level 73	Level 73	Level 75	Level 74	Level 75	Level 75
	Attacks: Fake Out U-turn Blaze Kick Close Combat	Attacks: Psychic Fangs Wild Charge Crunch Play Rough	Attacks: Accelerock Stealth Rock Stone Edge Play Rough	Attacks: Iron Head Brave Bird Body Press Light Screen	Attacks: Clanging Scales Aura Sphere Flash Cannon Clangorous Soul	Attacks: Wicked Blow Close Combat Poison Jab Iron Head
	Hold Item: No Item	Hold Item: No Item	Hold Item: No Item	Hold Item: No Item	Hold Item: No Item	Hold Item: No Item
						Gigantamax
Tower of Waters Beaten

Defeat him and you'll get his Rare League Card.

Following this, you can find Mustard in the dojo playing Pokémon Quest on his Nintendo Switch. Each day he will give you the opportunity to battle him again, with the same team as before