Dislaimer: I don't own Mario or Hazbin Hotel/Helluva Boss. Those belong to Nintendo and ViziePop. This story was inspired by a phenomenal piece of art, check it out!
Stone smoldered as wind wailed about the ruins of Peach's Castle. Stars glimmered overhead as the moon shone down on the burning inferno that once belonged to the royal family of the Mushroom Kingdom. It seemed to be hell on Earth, which Luigi thought was quite fitting for his final confrontation with Bowser. The Koopa King had murdered Mario, Peach, Daisy, and Toad a decade ago in a brutal execution that had been broadcast throughout the kingdom as Bowser's bloody, terrifying reign began.
Luigi vowed that day to avenge his brother, his sister in law, and his girlfriend, as well as everyone who had perished and suffered under the tyrannical reign of the Koopa King. That meant killing Bowser and everyone who served him. The koopas were extinct, followed by the goombas and Bowser's most trusted lieutenants, his own children.
A roar shook the still smoldering walls as Bowser leapt from the shadows and unleashed a torrent of flame at Luigi, who jumped to the side and pulled a potion from the pouch hanging on his hips and drank it. Engulfed by an orange and golden glow, Luigi flung an immense fireball at Bowser. A defaning boom rattled the walls of Peach's throne room as the fireball made contact, stripping away several chunks of flesh and shell from his opponent.
If Bowser intended to burn Luigi alive like he had his previous victims, or scare him by burning the scorching the castle walls, he would be sorely disappointed. The concoction was ancient and gave the former plumber hours long invulnerability to fire and the ability to use the Ignaris spell. It would burn not only flesh and bone, but the opponent's soul; hence why it was banned a thousand years ago. Bowser wouldn't be coming back, not this time.
The tyrant's eyes narrowed as he flung his flaming body towards Luigi with the intention to paint the now burning walls with his enemy's blood. Instead he slammed into the walls and roared in agony as part of the wall collapsed on him. He rose, bloody and smoldering, from the rubble. Shoving the pain down, he unleashed another torrent of flame and enveloped the entire throne room with the hottest flames he could. Luigi's laughter drove terror into the Koopa King.
Luigi summoned Ignaris again and lobbed it over his head, arcing it at the fiend. Bowser attempted to counter it with his flame breath to no avail as the fireball flew down his pillar of flame and throat. Ignaris exploded, sending Bowser's flaming remains scattering across the burning castle. The tyrant was vanquished, the long crusade nearly done. As the devastating fire burned the castle, Luigi turned, walked out, and never looked back.
Three days later
"I'm sorry for not visiting sooner brother, Peach, Daisy, Toad. I finally fulfilled my promise. I made him pay." Tears streamed down Luigi's face and for the first time in years, the former plumber let them fall. A gentle breeze caressed his face and caused ripples on the nearby lake. It had been their favorite picnic spot in the kingdom, and it only seemed fitting it should be their final place of rest. Perhaps out of respect, perhaps out of insanity, Bowser had buried them in separate caskets and kept them near the castle. It hadn't taken long after the flames died down to dig them up and relocate their bodies.
"I know you wouldn't have approved, brother. Mercy always stayed your heart, knowing that throwing him into lava or knocking him off the highest peak in the land would only keep him down for so long. He'll recant, you'd say, we have to give him a chance. You were always the hopeful one. The happiest day of my life is when you told me I was going to be an uncle. I wish things were different, Mario."
"Peach, you were a kind, strong soul. No matter how many times Bowser kidnapped you or take over the kingdom, you defiantly spat in his face every time. You never showed fear and always made the best cake. Being the best man at your wedding is the greatest honor I've ever known."
The words caught in Luigi's throat as he struggled to say farewell to the love of his life. Memories flooded his mind and opened floodgates as the steady stream of tears became a waterfall. "Daisy, I...I love you. Every day with you was a blessing and each day without you a curse. Rest in peace my love."
"You were one hell of a friend, Toad. It feels like I never thanked you enough for all the hard work you put in helping us over the years. Sure, you had sworn fealty to Peach and her family when you were young, but you went beyond the call of duty more times than I can count to help us bring her home and restore the kingdom. I know you held back during our tennis matches... thanks for letting me win."
A fifth spot with nothing but a pile of rocks and a hole lay in between Daisy and Toad. One day Luigi would forever sleep in that resting spot; until then, he would continue his crusade against Bowser's surviving minions. Those who had taken part in his loved ones' murders would get what's coming to them.
Luigi stayed until long after the sun cast its last golden rays and the celestial bodies in the heavens above came out to illuminate the night. They'd come for him one day and when they did he would accept his fate.
It was only a matter of time.