Author's Note: Special thanks to ManiacLove620 on AO3 for this idea!
Planned
Danny flew up to Clockwork's lair. The clock tower doors opened on their own as he approached, and Danny floated inside, landing on the floor in the middle of the main area. Clockwork, in the form of an old man, turned his attention away from one of his screens and looked at Danny.
"You got my message," said Clockwork.
"Yeah," said Danny, rubbing his arm and looking around. "Why did you ask me to come here?"
"Your ultimate enemy has resurfaced."
Danny stared at him a long moment before speaking. "You don't mean…?"
"I do."
Clockwork transitioned to his middle-aged form, and Danny continued staring at him, trying to process his words.
"But I sealed him in a Thermos," said Danny. "And you have the Thermos, don't you? Did he escape?"
"No," said Clockwork. "That particular version of your dark self is still sealed away and unable to harm anyone."
Danny breathed out a sigh of relief.
"This new version that has surfaced was created in a different way," said Clockwork. "But the end result was the same: His humanity was ripped out of him, and he merged with Vlad Masters' ghost half."
"Created in a different way," echoed Danny. "So not as a result of me losing my family and friends? Did this happen to another me in an alternate timeline?"
"No," said Clockwork, morphing to his child form. "His creation happened in your timeline."
"But how is that possible?" asked Danny. "That first version I sealed away was from my timeline, wasn't he?" He paused, dread filling his chest. "Are you saying that…that I turn into him again in a new way?"
Clockwork did not reply immediately. Danny's heart hammered as he waited.
"No," said Clockwork at last. "You do not."
Danny exhaled and nearly choked on his saliva. "Then what happened?" he gasped out.
"It's complicated," said Clockwork. "And I think the best way for you to understand is to talk to him yourself."
"Talk to him?"
"Yes. You must go into the future again and put a stop to his violence, just as you did before."
Danny stared at Clockwork, memories of facing off against his ultimate enemy clashing in his head. The adrenaline, the anguish, watching those sauce tanks explode and for that one small moment thinking he had lost his family and friends forever.
"I'm sorry to have to ask you to do this again," said Clockwork, his tone a little gentler. "But you're the only one who can. You know that."
Danny returned his attention to Clockwork and slowly nodded. "I do know that."
Clockwork raised his time staff. A portal materialized in front of him, an entry point into the future. Danny hesitated only a moment before sucking in a breath and soaring through.
He emerged out of the sky, above a haunted scene that resembled the one from his memories except that here, only his parents were strapped to the Nasty Burger sauce tanks with his older, darker self hovering before them.
Sam, Tucker, Jazz, and Lancer were nowhere to be seen. Why had his dark self chosen to target only his parents this time?
Let them die, Danny. For both of our sakes.
His first ultimate enemy had begged that of him, but he still had no idea why.
Danny clenched his jaw and started flying straight toward this current enemy.
"Hey, old man!" he shouted.
His dark self looked up at him, but his expression was not angry, only bewildered.
"You," he said simply.
"Yeah, it's me," said Danny, stopping to hover just a few feet above him. "I'm your past. But you're not my future."
His parents stared at him with wide eyes, their mouths covered with ghostly energy and unable to scream or call to him. Familiar, just as they looked the first time he faced his ultimate enemy. Only this time they were a decade older, their faces lined with age beneath greying hair.
His mom looked so terrified. He could see the tears shimmering in her eyes.
He didn't waste any time and sucked in a deep breath to use the only power he had that could defeat his dark self. He released it in a bellowing ghostly wail, shattering windows as his dark self was blown away, crashing into a building that crumbled to the ground on top of him.
Danny flew as far as he could until his head swam and he fell right in front of the wrecked building. His spectral form fizzled out as he dropped to his hands and knees in the street. He lowered his head, moaning and attempting to catch his breath. His wail still sapped so much of his energy.
His dark self's gloved hand broke through the wreckage, clenching into a fist as he pushed his way up and out. Danny looked up but was not surprised. He had replayed this scene so many times in his nightmares.
His dark self's suit was tattered and clinging to his bruised body, the flames on his head nearly extinguished. He panted and clutched at his chest, but he did not snarl as expected. His expression was somber as he stared at Danny, as if he were studying him.
"You look just how I remember you," he said quietly, weakly.
Danny pressed his hand to the asphalt and pushed himself up, his knees shaking as he forced himself to stand. "You mean you remember being me?"
"No. I was never you."
Danny tilted his head.
"You were wrong. What you said before." His dark self grunted and coughed. "You're not my past. You and I aren't the same person."
He looked down at his torn suit, his battered body. He gripped the front of his suit, the Phantom symbol emblazoned over his breast.
"I have memories of being you," he said. "But they're not real."
"What are you talking about?" demanded Danny, his skin prickling.
His dark enemy stared at him for a long, silent moment before slowly lowering his jumpsuit zipper and pushing his tattered sleeve off his right shoulder. The number 26 was tattooed in white on his upper arm.
Danny instinctively looked down at his own arm before returning his attention to his enemy. "I don't understand."
His enemy covered the tattoo again and zipped up his suit.
"What is that?" pressed Danny. "What does it mean?"
"One day you will see me again," said his dark self simply. "I won't look like this, but you'll know it's me when you see this number. And then you'll understand."
Danny stared at him a long time, unable to decipher his words. Was this some kind of trick?
It had to be.
Danny raised his Thermos and took off the cap.
"I wish you would just kill me instead," said his dark self, his voice tortured. "That was always my purpose. I was created to be used and then destroyed. To live a short time before she killed me."
Danny's hold on the Thermos faltered. "Who is 'she'?"
His enemy did not reply. Danny lifted the Thermos again and captured him inside.
The town fell quiet, nothing but the blowing wind and some rubble shifting in the wreckage before him.
Then all sound completely stopped. Danny looked up to find Clockwork in his middle-aged form holding up his time staff, his parents suspended in air above him, unconscious, unaware.
"I'll take that," said Clockwork, holding out his hand toward Danny.
Danny looked at the Thermos. "Who did I just trap in here?"
Clockwork's hand remained outstretched even in his silence.
"I know you know." Danny's voice was low, his teeth nearly clenching.
He stared hard at Clockwork, his eyes brimming with tears as he craned his neck to keep eye contact with the hovering enigma above. Clockwork's form shifted twice, to a child, to an old man.
"I'm not the one who tells you," said Clockwork.
Tears continued burning Danny's eyes, but he knew he could never make Clockwork tell him. He raised the Thermos and allowed Clockwork to take it from him.