To encounter Octo MC, simply "Challenge the skies" at any Statue of Griette. The next time you set sail for approximately one in-game day, you will encounter Octo MC. Solving his puzzle rewards a significant amount of gold, which increases as you progress through the campaign. Failing to solve his puzzle will result in the loss of 10% of your current gold.

Octo MC can only be challenged once every 14 in-game days.

To solve the puzzle, you must guess the sequence of three notes within five or fewer attempts. Notes cannot be repeated in the sequence.

After each guess, you'll get a hint:
✅ - Shows how many notes are correctly positioned in the most recent guess.
❓ - Shows how many notes in the guess appear in the solution, but in a different position.
❌ - Shows how many notes in the guess do not appear in the solution.

To use this guide, you can always start with the guess of GREEN, RED, BLUE and follow the flowchart. This will always solve the puzzle within 5 guesses.

Because there is no consequence for using all 5 guesses, for simplicity, this flowchart will "brute-force" the solution when there are enough remaining guesses to do so.