Geass

Geass is a mysterious ability which certain people can bestow upon others; C.C. is the most prominent character who grants the power of Geass. The Geass manifests differently in each individual, possibly related to their inner desires and personality. The power of Geass increases with use, and should the user lack the willpower, they may be consumed by it, which was the case with Mao. C.C. calls Geass the Power of Kings, and though she is unable to use the power herself, she is immune to the power being used on her. In the final episode of the second season, Lelouch states that the Geass is a form of wish (referring to himself and C.C.). However, people who have Geass are not immune to the Geass effects of others. The Geass is represented by a glowing, bird-shaped symbol.

Every Geass, while powerful, has its own unique set of restrictions, limitations, or idiosyncrasies. These factors allow a Geass to be defeated, or its power limited, by someone who is aware of its characteristics. All Geass abilities that have thus far appeared within the canon of the television series have been related to the mind, influencing such things as will, thought, memory, and perception. Geass abilities in the alternate universe manga Nightmare of Nunnally have no such limitations. All Geass, regardless of user, appear in only one eye in the initial stages. Eventually, assuming the user lives long enough, the Geass will eventually begin to grow until it shows on both eyes, seemingly as a result of repeated use, or pushing the Geass to exceed its own limits. However, overuse and/or mental instability can lead to an affliction called "Geass Runaway", causing the user to become unable to control their Geass, making it become permanently active.

The only case of a "perfect" Geass in the series is Charles zi Britannia, who shows the ability to activate his Geass at will, yet possesses Geass in both eyes. Once the Geass evolves to two eyes, the person who gave the Geass can grant the user his or her 'Code', thus removing the Geass and making the user an Immortal and immune to all Geass, and the person who gave them the Geass usually dies after granting a person his or her 'Code', though in both cases shown, this has been a result of fatal wounds - V.V. had yet to regenerate from the wounds he received when his Siegfried was destroyed, and the unnamed nun in the flashback apparently committed suicide.

Following the assault on the Geass Directorate launched by Lelouch and the death of the other remaining Geass users, Lelouch became the only person still having the power of Geass, other than Rolo, while C.C. became the last human still having the Code after Charles is absorbed by the collective unconscious, and V.V. is killed by Charles. There is only one instance of a person overcoming the effects of Geass, which is the case of Nunnally - Lelouch attributes this to a very strong degree of will power, which may have been helped along by Charles being dead by then, though there is no mention of her recovering the lost memories of her mother's death, which was Charles' "primary" ability.

According to an English edition of Newtype, the power of Geass has something to do with the very existence of humankind, and it may be used to destroy or transform just about anything. This is because the "gods" of the Geass universe are actually a collection of subconscious and will that are always in conflict, and one with a powerful Geass could influence it, as Lelouch does in the series, and Charles seemingly does, and with a proper system, can also influence reality, which is the concept behind the Sword Of Akasha. "Geass" may be an intentional corruption of the word geas or geis, a term for a type of magical contract in Irish mythology.

Geass in ancient mythology
Geass originates in Gaelic mythology and is in many ways analogous to the Greek and Roman concept of the tragic flaw. One of the first and best known heroes subject to a Geass is the central character of an Irish mythology Ulster Cycle, Cú Chulainn. He was subject to a 'Geis' of being forbidden to eat dog meat by his enemies. But in early Ireland there was a powerful general taboo against refusing hospitality, so when an old crone offers him a meal of dog meat, he has no choice to break his Geis. In this way he is spiritually weakened for the fight ahead of him.

In Code Geass, Geass is a power given to Lelouch by the mysterious C.C., it allows him to force others to do his will to certain limitations. The similiarity to the Geis concept is evident and presumably the reason behind its name.

Geass Canceler

 * A peculiar Geass-related power given to Jeremiah by Britannia's Geass Directorate, Jeremiah's Geass Canceler manifests in his left eye and unlike other powers of Geass is represented by an inverted blue version of the bird-like Geass sigil. As Jeremiah's left eye was shown to be a cybernetic replacement in his final appearance in the first season, it is assumed that this is also a cybernetic eye, raising the question of whether or not Britannia's Geass Directorate had managed to reverse-engineer Geass, or had simply been developing countermeasures. This ability appears to cancel out all other Geass effects within a given range, hence the name "Geass Canceler". It will automatically reverse any Geass used on Jeremiah.

Nunnally's Geass

 * Upon contract with the entity known as Nemo, Nunnally and Nemo gain the shared ability to read "the lines of the future", functionally identical to precognition. A red, bird-like sigil lights up in Nemo's left eye when the ability is activated.

Alice's Geass, "The Speed"

 * Implanted with cells from C.C., Alice obtains a Geass ability referred to as "The Speed," which allows her to hyperaccelerate all objects within a given radius by manipulating local gravitational pull. When active, a Geass sigil appears upon Alice's forehead. A cell-action suppressant limits this ability, as the activity of C.C.'s biological matter tends to strain and overtax the human body. The suppressant can be neutralized to give Alice access to the full power of her ability, enabling movement of such high speed that it resembles teleportation.
 * Alice uses this for a variety of purposes. In Code 3 'Evil Instrument Nemo', she protects Nunnally from Ekaterina Sforza's bullying by stealing her skirt (Bandai Manga Volume 1, p.91).

Sancia's Geass, "The Order"

 * Sancia's Geass accurately identifies the positions of targets within a given range and precisely calculates their probable movement trajectories based on all known variables. When active, a Geass sigil appears on Sancia's forehead.

Lucretia's Geass, "The Land"

 * Lucretia's Geass allows her to map three-dimensional terrain accurately within a given range. When active, a Geass sigil appears on Lucretia's forehead.

Dalque's Geass, "The Power"

 * Dalque's Geass augments her physical strength by exaggerating the magnitude of macroscopic forces. When active, a Geass sigil appears on Dalque's forehead.

Mao's Geass, "The Refrain"

 * On meeting another's eyes with her left pupil, Mao is capable of reading memories or forcing a victim to relive past experiences, not unlike the drug by the same name. The ability was obtained as a result of an implant of C.C.'s cells, and its use results in rapid cellular degeneration. Massive amounts of cell-action suppressant are required to keep this process in check.

Rolo vi Britannia's Geass, "The Ice"

 * Rolo's Geass allows him to freeze anything in his area of effect, even time (probably a reference to his anime counterpart's Geass). He can also use it to directly freeze a target's Knightmare Frame and pilot.

Charles zi Britannia's Geass, "Wired Geass, The Dead Rise"

 * Charles Geass allows him to resurrect the dead as his slaves. It is also a Wired Geass, meaning he did not make a contract to obtain it. He first used the Geass when he and his parents were murdered, allowing him to obtain immortality. A Geass sigil appears in his right eye when he was seen using it in a flashback.

Marianne vi Britannia's Geass, "The Soul"

 * Marianne's Geass is the same as it is in the anime, allowing her to transport her soul into another person's body.

Lelouch and Nunnally vi Brittania's Geass, "Wired Geass, The Zero"

 * This Geass is described by Nemo as "the power that returns all creation into nothingness." Lelouch seems to manifest his as a kind of obliteration attack launched by contact of his hand to something, such as a Knightmare. It causes massive damage and destroys it infinitely. It has only been resisted twice, by Suzaku in the Lancelot and by Bismark Waldstein, since he is an undying warrior brought back by Charles' Geass.
 * Nunnally's version of "The Zero" is described as the key to Eden Vital. It can open the "door to heaven", creating a portal to Eden Vital which Charles, Marianne, and C.C are planning to use to collect the conciousness of humanity back into a single entity and kill God.

Castor rui Britannia's Geass (DS Game)

 * Castor's Geass is called "Bless." It is "the power to force your own thoughts into others" and can be used both for telepathic communications and to make people have headaches.

Pollux rui Britannia's Geass (DS Game)

 * Like his twin brother, Pollux's Geass is also called "Bless." He can persuade others to do his bidding just by saying "God bless you."

Rai's Geass (Lost Colors PS2/PSP game)

 * The protagonist of Code Geass: Lost Colors, Rai possesses a non-optical manifestation of Lelouch's "power of absolute obedience," which relies instead upon the sound of his voice as a medium. The ability cannot influence the same individual twice, but those formerly afflicted by Lelouch's Geass may still be controlled, and vice versa.