Technically it wouldn't be a leak : nothing has leaked 343 offices due to a few mole or an informer of a site, but it was the developer himself inadvertently publish information. Among many things shown in the last video-documentary of Halo 4 , A Hero Awakens , around minute 3:55 appeared for a split second a full document text. Someone has so intrigued and decided to block those frames, zoom in and read what there was on the document: it was a piece of script for motion-capture actors, which is even revealed the main enemy in what appears to a climax of the game.

At this point is obviously required a nice, giant phosphorescent, ...

SPOILER WARNING

We don't know if 343 have introduced intentionally such information in the video knowing that someone would have found increasing the noise level around the game, but it's revelations of a certain thickness that you might want to avoid in order not to ruin the surprise of live events in the game. Users warned ...

Sietete still here? Ok, let's move on then. Parts of the script that you can read snippets are these:

"If you don't mind ..." Cortana appears behind the Teacher.
[testo illeggibile] all Cortana that emerging from the bridge
"Compassion for humanity is misplaced."-Teacher
"I'm doing for mankind." Chief loads the Teacher.

runs towards the teacher and jumps on all its parts (legs, arms, torso, back)
Several copies of "Cortana" cling and climb on various objects at great speed.
The Teacher is attacked by Cortana. Tries to defend itself is pushed in.
The Teacher expands his fist and drops Chief.

Cortana starts trattenenre the Teacher by locking his limbs at the bridge.
-Several copies of "Cortana" climb the actor of "Teacher" and then ...
[testo illeggibile] a specific part of the body (head, back, sues, knees, elbows, shoulders)
-The Teacher she immobilizes effort.

Chief is free
-Laying of Chief locked
-Chief falls, lands on the Board
-Chief hanging motionless

From this we derive a fundamental scene information: our enemy in the game will be the Teacher , former Supreme Commander of the army of the precursors and activator of the rings during the war against the Flood, which speaks in terminals of Halo 3 , those of Halo CE Anniversary and in the novel Cryptum . The ultimate fate of the Teacher is not known: apparently he had hidden in a millennial sleep on Requiem, the planetoid which come Master Chief and Cortana in Halo 4 . That is really him the ancient evil awakened, which references the famous phrase "An Ancient Evil Awakens"?

Other information is very interesting for Cortana: apparently, due to changes caused by contact with the rings, has acquired the ability to create multiple copies of itself which may also interact physically with the real world, fighting together with Master Chief or at least assisting him in some situations.

But it doesn't stop there: Amazon has made price list the next novel in the Halo saga, The "Thursday War" , also by posting some excerpts. These have emerged more information gathered by always very careful NeoGAF users. There below the list, obtained by combining the information obtained by script just discussed.

• When Master Chief wakes up early in the game, Forward Unto Dawn is arrembata by a group of Covenant-are trying something, but not the Chief.
• The Covenant belong to a particular religious faction led by the Elite and they arrived on Requiem for an armoury of precursors.
• The Covenant believe that Requiem is the place where a living God-want to find him and wake him to use it as an ally in the fight with humanity.
• The main enemy is the teacher, an ancient forerunner. It is the being that the Covenant believe being a God.
• The D.ssa Halsey, also seen in Reach, makes its appearance in Halo 4 when Chief asks her to find a solution to the "problem" of Cortana.
• A character has, or appears to have telekinetic powers

And that's it. If you have read everything here, the comments area is at your disposal to discuss these revelations.