Warrior Orochi 3 Ultimate is absolutely packed with secret characters from across the Dynasty Warriors and Samurai Warriors series, and even a few new additions. Hundun is one of those new characters, based off of a mythological Chinese figure considered to be the source of all chaos.
Hundun is a lumbering Power character that can easily destroy hordes of enemies with his attacks. The character can only be unlocked by playing Unlimited/Gauntlet mode. This randomly generated mode consists of different levels, or layers, and each layer is made up of different battlefields with different difficulties. Gauntlet Mode can be punishingly difficult so you’ll want to make sure to train up a party of characters in story or free mode first, with high levels up the 90s and 100s.
The only way to obtain more characters for the mode is by defeating them in battle during Gauntlet Mode, where they’ll drop a green diamond. This can be turned in at the end of the stage to obtain the character as a Sworn Ally. There’s also a chance you could get a Sworn Ally by opening a treasure chest.
In order to unlock Hundun, you’ll have to make it to the 4th layer your first time through Gauntlet Mode. Once you beat him in battle, you’ll unlock the character for use in not only Gauntlet Mode, but also Story and Free Mode. It may take you a while to train characters up and make it through Gauntlet, but the payoff of obliterating enemies with him will be worth it.