"BERSERK and the Band of the Hawk - Additional Scenarios DLC - Berserk Musou
I tried my best, ahaha
This armor is Guts’ most powerful outfit in the game that keeps him in instant Berserker mode. It’s faster and capable of building up its Frenzy and Death Blow gauge rapidly. You also get the Full Barrel Cannon Blast Sub-Weapon, which is one of the best in the game as it deals massive damage, even to bosses. The trade off for all the speed and power, though, is that you can’t use your horse. You can unlock this outfit by completing 100 Layers of the Endless Eclipse mode using Guts."