Earth Ark

"All that stuff was going to culminate and end on Earth. And it was going to be the end of Halo. We had no plans to do another game after this. It was like: this is how Halo ends."

- Martin O'Donnell describes the intended Earth Ark level.

"Earth Ark" was the working title for a series of three campaign levels cut from Halo 2. The three missions would have served as the penultimate in the game, showcasing the Master Chief's return to Earth and the final stand of the Prophet of Truth.

Overview
While making Halo 2, Bungie developed pairs of levels under single names - such as Outskirts and Metropolis being originally created as one level named "Earth City". Earth Ark was seemingly similar in this regard, seemingly intended to comprise of three individual missions in which the player would alternate between playing as Master Chief and the Arbiter (then-known in development under the name Dervish).

Battle on the plains
In the first of the two levels under the "Earth Ark" heading, the player would play as the Master Chief. The mission would open with the Spartan aboard the Prophet of Truth's Forerunner ship as it emerged from slipspace over Earth, having just escaped the Fall of High Charity to the Flood. Master Chief was to communicate with Lord Hood, before using a grenade to blast a porthole off the Forerunner ship and jump out of the ship over Earth.

Facing down Truth
When describing this level, Joseph Staten also noted that the level would have featured a "trench run" for the player to make their way onto the Ark. It is unclear whether this trench run was intended to refer to the aforementioned Phantom cutscene, or whether it was intended to include a new gameplay element following the Arbiter's Phantom disappearing into the trench. After the end of the aforementioned cutscene, the player was to switch to the perspective of the Arbiter for the final mission of Halo 2, possibly including some combat inside the Ark. The next set of revealed storyboards showcase the interior of the Ark, with the Prophet of Truth scrambling to activate the Halo Array. Truth and the Arbiter would have a brief dialogue concluding in the Arbiter removing his helmet and throwing it to the ground near truth, before raising his weapon and pointing it at the Prophet. Gameplay would then commence with a final boss battle against the prophet. During the dialogue, the Master Chief and 343 Guilty Spark would arrive in the control room, possibly indicating that the Master Chief would serve as an NPC ally in the encounter.

Escaping the Ark
The final cutscene of the game then shows Master Chief running to escape the collapsing Ark structure before being swallowed in a bright light. The scene then transitions to the interior of the Torres Vedras (the name for what would be later named Cairo Station in final release), with Master Chief being awarded a medal by Lord Hood. Several strike fighters begin deploying fireworks outside the station and the crew applause. As the Master Chief looks out over Earth, he shares a few words with Johnson before Johnson departs and Miranda enters the frame. The cutscene ends with John-117 and Miranda Keyes watching over the Earth from orbit as the Covenant fleet prepares to leave the system.

Epilogue cinematic
In these early drafts of Halo 2, the game's after-credits tease cinematic was intended to be the same as the one featured in the final game - even despite Bungie's intentions to move onto a new non-Halo game entirely. The cutscene, depicting the Flood overtaking High Charity and Cortana being trapped with the Gravemind, was always intended.

Legacy
Earth Ark - and the original Halo 2 ending as a whole - did receive some development and gameplay prototyping internally, though ultimately had to be cut due to the development hell which Halo 2 went through to reach ship. As of 2016, composer Martin O'Donnell still has the original script and voice lines written and recorded to support the ending. Due to the ending being cut down, Halo 2 received backlash from the fanbase as a whole, with the game being infamous for the abrupt conclusion to the game. As such, the events surrounding Earth Ark would be kept shrouded in mystery predominantly until the 2020 release of many of Halo 2's storyboards by artist Lee Wilson.

Despite being cut, many elements of the original ending of Halo 2 were later reused as inspiration for Halo 3. The concept for the Ark on Earth (itself based on a structure concepted and modelled by Marcus Lehto during the early production of Halo: Combat Evolved) was repurposed in Halo 3 for the portal structure around which the first half of the game is set. The Master Chief's peril aboard the Forerunner ship was later made the subject of the comic series Halo: Uprising, while the Master Chief using a Forerunner door as a heat shield to land on Earth would be directly used in the opening level of Halo 3. The Master Chief's emergence from the dust behind the Marines would later be seemingly reused in the Halo 3 announcement trailer.

A screenshot published in The Art of Halo: Creating a Virtual World, page 31, showcases a Jackal Major inside a Forerunner environment with the book's caption labelling it as an environment on Earth. It is possible that this screenshot was taken in the cut Earth Ark level geometry.