Difficulty Settings Unlocked
Since Legendary is the hardest difficulty setting for Halo, completing any stage with this difficulty allows you to replay it on any lower difficulty setting.
Ending
The ending begins with the Master Chief running toward his spacecraft and escaping Halo.
Scene Cut from Ending
On other difficulties, after the chief escapes, you view a scene with the Flood wandering around the Pillar of Autumn before it explodes. The Legendary ending cuts this scene.
Alternate Scene
In the place of the cut scene, you see a blue Covenant Elite trying to pull away the Sarge's assault rifle. When they both see the Pillar of Autumn begin to explode, they stop fighting and the Elite lets go of the rifle. Then, the Sarge says, "This is it, baby. Hold me," and they hug each other.