There are five reversed messages in the Halo series, one in Halo 2, one in Halo 2: Anniversaryand three in Halo 3.

Destroyer's Invocation Message Edit

In the Halo 2 song Destroyer's Invocation, (the first movement of the Mausoleum Suite on the Halo 2: Original Soundtrack, a mysterious voice chants. If this mumbling is reversed (listen), a voice is heard saying:

I live to see death and destruction, evil... over the light, but the light cannot be extinguished.
I live in a prison of my own demise.
I am time

The voice can be heard during the cut scene before The Arbiter, the level Gravemind when you rescue the Marines, and during The Great Journey when you fight Tartarus.

Recently, Marty O'Donnell posted on the Halo.Bungie.Org forums that he wondered "why the transcript (of the reversed message) is still wrong." This seems to indicate that changes must be made to the transcript before it is accurate.

There are many theories as to whom the voice belongs. The most plausible candidate is 032 Mendicant Bias, however, other possibilities include a Prophet or the Gravemind. When played, it seems to sound like the Gravemind, but when sped up slightly, the voice seems to belong to the Prophet of Truth. If sped up even more, the voice resembles that of a Monitor.

There are voices that sound like another reversed message in the "infected" part of the Mausoleum Suite, but so far they seem to be indecipherable (too distorted).

Black Tower Message Edit

In the Halo 3 soundtrack, during the first few minutes of the track Black Tower, there is yet another message that can be heard if you reverse the song. Here is a transcript:

Eyes from Death's dream kingdom,
Appear as sunlight on a broken column.
There in Death's other kingdom walking alone,
Trembling lips form prayers to broken stone.

This message appears to be a reference to T.S. Eliot's Poem, The Hollow Men. The first part of the transcript refers to lines 20-23.

In death’s dream kingdom
These do not appear:
There, the eyes are
Sunlight on a broken column

The second part refers to lines 47-49.

Waking alone
At the hour when we are
Trembling with tenderness
Lips that would kiss
Form prayers to broken stone.

It is also worth noting that a line (or lines) from the last stanza in T.S. Elliot's The Hollow Men was used in the end of the Halo 3 E3 2006 trailer. The Stanza is as follows:

This is the way the world ends
This is the way the world ends
This is the way the world ends
Not with a bang but a whimper.

Dread Intrusion Message Edit

Also in the Halo 3 soundtrack, a reversed message can be heard in the tracks Gravemind, and Dread Intrusion. The entire message is currently unknown, however, several lines are intelligible. Oddly, the voice during these messages sounds different from Gravemind. It echoes considerably, rendering several lines unknown, it is much deeper in pitch, and multiple other voices can be heard. This could be a reference to multiple Graveminds from the past that speak as one because of inherited knowledge. The first two lines both have 7 syllables each, a possible 7 reference.

Side by side, we march as one,
Humans and Elites will die,
The Earth will fall if we strike together,
So forth shall all of life.

The exact person who is speaking is unknown. Just like the Destroyer's Invocation Message, there are many possibilities about who it could be. The likely candidates are the Gravemind and the Prophet of Truth, since only Elites and Humans are mentioned.

A voice can also be heard on the level, The Covenant. It can be found on the third tower's control room, where there are Brute Stalkers.

Cryptic Whisper MessageEdit

In Halo 2: Anniversary, a message is included in the track Cryptic Whisper, the remastered version of Destroyer's Invocation.  Reversed, it says:

We squander eons in the darkness,
While they seize our triumphs for their own.
The Mantle of Responsibility, for all things, belongs to Forerunners alone.
Think of my acts as you will.
Do not doubt the reality:
The reclamation has already begun.
We are hopeless to stop it.

This is a reference to the Ur-Didact's speech in the Epilogue of Halo 4.
