Octopath Traveler is a hard, gritty, JRPG filled with immense challenges and a great story.
The game is a challenge from start to finish. Players have to grind for hours on end to level up their characters as much as they can to challenge some of the big bosses that litter the world.
Once you level up enough, unlock all of the secret jobs, and do everything the game has to offer, it feels like there's not much left in the world to discover—but you'd be wrong to think that. There's one big post-game dungeon awaiting anyone with the willpower and tenacity needed to challenge it.
Spoiler warning: Huge spoilers for the post-game dungeon and the entire game are listed below. If you don't want to ruin your experience in-game, please come back to this section when you're ready to proceed.
You've been warned.
To unlock the post-game dungeon, you'll first need to beat all eight character stories and defeat the eight final bosses. There are four chapters in total for every character, so you're looking at beating 32 chapters in total.
You'll then want to complete two subquests for Lyblac and Kit, called Search of Father and Daughter of the Dark God, respectively.
Search of Father
Once you complete your first character's tutorial, you'll encounter Kit outside of the city and will instantly give him a Healing Grape. Afterward, you'll meet him again in Noblecourt, where he'll ask you to Allure or Guide a theater member toward him. You can find this theater NPC one screen to the right, called "Aspiring Actor."
After completing that, you'll meet him next on Moonstruck Coast and will need to bring him a Lapis Lazuli to finish the quest. You can get a Lapis Lazuli from a merchant at Grandport through buying or stealing it with a character's ability.
Daughter of the Dark God
You can start this quest in Bolderfall by talking to a guard that's head-over-heels for a dark-haired women outside Ravus Manor. You'll need to challenge him using Olberic or H'aanit's ability and win the match.
You'll then need to head to Saintsbridge where you'll find the soldier still stalking the women. Have a character either steal or purchase the poem from the same soldier and head to Saintsbridge's cathedral to find the women, who's named Flora.
Give her the poem and it'll complete the quest.
The Ruins of Hornburg
After completing the two subquests and main missions, the last thing you need to do for the quest is head to West S'warki Trial and find the Impresario. After talking to him, a small mini-boss fight will begin. Once you win that fight, you'll unlock the final dungeon.
Now here's where the fun begins. The Ruins of Hornburg is the hardest dungeon in the game. You'll need to go through a boss gauntlet including more powerful versions of all eight final bosses without having an option to save or leave the area to buy items. There's also a final boss awaiting the end for anyone strong enough to complete it.
Beating each boss will reveal new information about the world's lore and is a challenge worthy of any player looking to prove their might.