Tuba Trio

"'Well, young maestro.. there's nothing I can say this time, but I'm 100% sure you're not ready to fight all three of them at once.'"- The Merchant

Considered to be one of the hardest boss fights, the Tuba Trio consists of the tuba knight, the tuba lunatic and the tuba demolitionist after they were defeated by the player in earlier stages of the game. Now immensely more powerful than their predecessors, it is almost impossible to win the fight alone and thus you start the fight by trying to survive until the Tuba Merchant arrives in order to assist you in battle, giving you a tough but fair fighting chance.

Background
The fight is unlocked by defeating the three bosses Tuba Knight, Tuba Lunatic and Tuba Demolitionist, and is started regardless of if you spared them before or not. In this iteration, they are nearly invincible, gaining a massive amount of armor and magical resistances while also increasing their damage done in comparison to how strong they were previously.

In order to win the fight, you are forced to remain vigilant and survive for a total of 181 seconds after which the Tuba Merchant will show up in order to assist you "This one time and one time only". If you previously managed to gain the companionship of the Tuba Horseman, he will also join you in battle. However, unlike the Merchant, he will only take a passive role and get you out of sticky, life-threatening situations that you maneuver yourself into.