First, you will have to defeat three "fast" Slowpokes. These fast paced Pokémon can be found on the calming wetlands just north of the dojo. Look for the giant dust cloud, then pass the 'fast' Slowpoke as they run through their loop (no need to chase them; they run a set route). These can be deleted like any other Slowpoke, you cannot capture them. Return to Mustard in the dojo after all three have been defeated.
Now mustard will want you to pick wild mushrooms from the warm-up tunnel even further north. You'll have to navigate through Concentration Forest and Practice Lowlands to reach the tunnel, but you shouldn't get lost as long as you follow the path to the bridges. If you need more advice, check out our guide to mushrooms here (and if you want more after the trial, this guide will serve you well).
Once you've returned to the dojo with the fungal fruits of your labor, you'll be tasked with the final and ultimate test: defeating your rival in battle (Avery or Klara, depending on which version you're playing). Neither is that complicated, and their Pokémon should all be weaker than yours.
Once you've won the battle, talk to Mustard in the dojo, who will finally reward you with the dojo's “secret armor”. This is Kubfu, the cute brawling bear. Evolving it won't be easy, and you'll first need to visit three highlighted locations (there will be exclamation marks for each on the map) on the Isle of Armor before unlocking the Water Tower. and the tower of darkness. Completing a tower will evolve the Kubfu, but you will need to choose wisely which one to approach, as this will determine which evolution will become your Kubfu. Additionally, you'll want your Kubfu to be at level 70, lest you like getting your ass kicked.
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