Cryptic Messages

The Cryptic Messages refer to a number of images and texts scrawled into the cell of Abstergo Industries' Rome facility's laboratory by one of its occupants, Clay Kaczmarek.

Abstergo
When Abstergo Industries finally recovered the information they needed from Subject 17, Desmond Miles, they left him in the Abstergo laboratory. Alone, Desmond discovered he had gained Altaïr's ability of Eagle Vision through the Bleeding Effect, which enabled him to perceive a number of markings around the laboratory and within his bedroom. Desmond quickly realized they were painted in blood by his predecessor in the Animus. Known only as Subject 16, this man was in the Animus so long that he went mad and took his own life after he drew the symbols.

Messages
The messages appeared along the walls and floors of the Animus room, and above Desmond's bed in his quarters.

Glyphs
When Desmond next entered the Animus, he discovered the messages were pointing him to files that Subject 16 had secretly planted in the Animus software. Once unlocked, these files provided information about the Templars, Assassins and Pieces of Eden throughout history.

Trivia

 * When Desmond slept between Animus sessions in Assassin's Creed, and during the introductory narration of Assassin's Creed II, there were flashes of the cryptic messages.
 * At the very start of Assassin's Creed II, if the Animus lab was viewed with Eagle Vision, all of the cryptic messages from the ending of Assassin's Creed were present, with the exception of the "Pyramid of Letters" and the "Barcode & Date".
 * During the infiltration of the Abstergo facility in Rome in Assassin's Creed III, Desmond was once again able to see the cryptic messages using the Eagle Vision. The "Pyramid of Letters" and the "Barcode & Date", were once again present.
 * The 'Eden Pyramid' and 'Letter Square' symbols also appeared in the Lair of Romulus of Catacombe di Roma in Assassin's Creed: Brotherhood, although it is not clear who left them there.
 * The mention of "Quetzalcoatl's hunger" is likely erroneous; though many Mayan gods demanded human sacrifice, Quetzalcoatl hated the practice.