A/N: shouldn't be doing a second Halo/cartoon crossover, but I want to. Disclaimer on muh profile.

Halo: Invasion

Prologue

Thomas Lasky stood on the bridge, waiting for the UNSC Infinity and the 2nd Fleet to emerge from Slipspace. The war against the Reach was nearing its end, the Didact and his Covenant forces already engaging the Reach's final armada beyond Harvest.

"How long until we exit Slipspace," he asked.

"Ten minutes, Captain," Roland, the ship AI, said. "Should I tell the SPARTANs to get ready for a boarding party or let Palmer deliver the message herself?"

"No. The Didact already has his mind set on destroying every single ship they have. I'm not going to risk SPARTANs with a Forerunner set on genocide." Lasky stepped away from the holo-table before Roland could protest the Didact's decision. FLEETCOM had already tried to convince the ancient alien otherwise, but he claimed the Reach violated the Mantle of Responsibility, the guide for the Forerunner and what the Librarian believed humanity would inherit. Their alliance was shaky, formed because of a common foe, one that believed they were the final authority of the Universe. Conquers of a Million Stars.

"Exiting Slipspace," a bridge officer shouted. The murky blue of Slipspace gave way to the sullen black darkness of normal space. Hollowed out Reach cruisers floated in formation, a few still burning. A hundred thousand kilometers away was the Didact's Fleet, forcing the Reach back towards a looming ring, twice the diameter of Halo, but thinner.

"Roland, can you identify the object behind the Reach?"

"No sir," the AI said. "We're so unfamiliar with Reach technology I can barely tell the difference between all of those 'Beetles' they deployed on Requiem." Images of oversized monsters flooded his mind. They had scared him. Last time he had been that scared was the Covenant attack on the Corbulo Academy.

"Don't talk about those," Commander Palmer said. "They took out a number of my SPARTANs, all good men and women. We all know the Chief and his Prometheans did saved humanity. Just like against the Covenant on Halo."

As part of the alliance with the Didact, a group of Promethean Knights were loaned to the UNSC, put under the control of the only human the Forerunner would dare call 'Reclaimer': the Master Chief, John-117. With the mechanical warriors, the Chief grew from legend to myth, appearing only when needed with his monstrosities. When the Reach begun a counterattack over Requiem, an offensive was launched to capture high-ranking officers. Inside, they came across a group of warriors, larger and tougher than the average SPARTAN. They slaughtered marines and gutted Fireteam Castle and Gypsy, until the Chief stepped in, killing the two he faced.

The scarabs that powered the creatures were destroyed by the Didact, using Forerunner tech that had gotten the eggheads excited. Who's now blasting apart an entire civilization. Lasky shook his head. They should consider themselves lucky we let them be annihilated by our ally. We wouldn't be as kind.

The Didact sneered when a portal opened up behind the Reach fleet. He had less than 150 ships to destroy before finishing the task he had set to. He had fled to the dark corners of Forerunner space after his defeat above Earth. There, he had rebuilt. His people had been lazy in their final days, leaving much of their technology lying around. Some, like the Covenant that now served as his Hand, did little to change the technology. Others, such as the humans, improved upon it. Yet the Reach used it to violate every principle that made the Mantle of Responsibility so important.

For that alone, they deserved death.

He ignored the arrival of the humans. He knew the Reclaimer was with them, bearing Promethean Knights forged from the Warrior Servants that had served the Didact near the end of the Forerunner-Flood War and survived the human's rampage across Requiem and the destruction of the Composer.

"Open a COM with the Infinity," the Didact said to his ship. A hologram of Captain Lasky appeared.

"Didact," the human said. "How can I help you?"

"Captain. I request the Reclaimer. I am going through the portal and I don't want to take chances with any Beetles the Reach haven't thrown against us."

Lasky frowned, discussing with the SPARTAN commander. "We'll be sending Fireteam Crimson alongside the Chief. Give us fifteen minutes to deliver them."

"You only have ten. The Reach Armada will soon be either dead or on the other side. My Hand will help you reactive the portal. However, I must get through before they shut it." Lasky nodded.

"I'll see what I can do. Infinity out." The holographic human disappeared. The Didact's ship continued to destroy Reach ships. However, for every one he dealt with, three escaped into the portal.

"Incoming human craft. Classification Pelican Dropship 79 Heavy-Troop Carrier."

"Let it aboard," the Didact said. "Give them an easy path to the bridge. We cross when they arrive." He watched as the last twenty ships of the Reach made their approach into the portal. He pursued, the CCS battle cruisers sweeping up the remainder of the enemy fleet. Jul M'Dama had strict orders to work with the humans until the Reach was extinct. Librarian, wife. Why did you catalog their kind? Why not leave them to perish alongside the Flood they are so like.

"Sir," his ancilla began, "the Reclaimer and his allies are almost here. Should I prep for the jump into Universe DC-16-52?" The ancilla said nothing about the jump location being strange.

The Didact frowned, listening as the door opened and the humans entered. "Make the jump. They can't get away." The ancilla nodded and the Forerunner ship entered the portal.

A/N: Sorta 'eh' on the end, but this is the most logical place. Note for YJ only fans: we're about to come upon the events directly leading to episode 210, "Before the Dawn".