Tarot

Tarot (タロット) refers to a group of playing cards which were used in Europe from the mid-15th century onwards, for both games and divinatory purposes. Different variations have been created by certain people, including Aleister Crowley.

In Toaru Majutsu no Index, Tarot cards are used as the basis for certain forms of Magic, in particular that of Golden-style Magic.

Principles
A deck of Tarot cards consists of 78 cards divided into two categories, the Major Arcana of 22 trump cards and the Minor Arcana of 56 suit cards. Each of the 78 cards carries a certain set of potential meanings, symbolism and interpretations (and in some cases, misinterpretations), some of which differ between versions.

The meanings represented by the cards change depending on several factors, such as the type of spread being used, the positions of the cards in the spread, their positions in relation to another, and the orientation of the cards, either upright or reversed.

Using these factors, Tarot cards can be used for Magic in many different ways. For example, using a certain card after another can strengthen the useful symbols of the first card, or the troublesome ones, and a reversed card, though perhaps yielding troublesome symbols, could be used to take advantage of the affinities between the four elements.

Major Arcana
The Major Arcana (大アルカナ) is the first category of cards in a Tarot Deck, consisting of 22 trump cards numbered from 0 to 21. Each of the 22 Major Arcana is associated with one of the pathways connecting a sephira on the Tree of Sephirot.

Of the Major Arcana, only The Hanged Man (吊られた男(ハングドマン)) has been seen used in Toaru Majutsu no Index as of yet, used by Leivinia Birdway. A combination of the Major Arcana from the Fool through to the World is apparently capable of greatly increasing the user's parameters temporarily, enabling them to execute supersonic movements.

Minor Arcana
The Minor Arcana (小アルカナ) is the second category of cards found in a Tarot deck, comprised of 56 cards divided in four suits; Cups, Swords, Wand and Coins. Each suit is comprised of 4 court cards; a King, a Queen, a Knight, and a Page, as well as number cards from Ace (1) to 10. The suits also have a specific element and colour associated with them. Rather than connecting directly to a sephira like the Major Arcana, the Minor Arcana are used to produce symbolic weapons of their element.

Golden-style organizations make use of the Minor Arcana cards which have been optimized to be used as symbolic weapons that activating a spell associated with their element. Though they share the same attribute, these symbolic weapons are not all equal. The ones with greater numbers aren't necessarily stronger than the ones with lesser numbers - the number changes the power that manifests, meaning each card activates a different spell.

These cards are generally instead to be used in large-scale ceremonies rather than in battle. However by activating the cards reactively in order within an area, as though one were randomly flipping them up on a table, a "table" dyed in the attributes of a suit can be prepared for such a ceremony. With a chain of multiple cards complete, a Golden-style ceremony can be carried out to draw in Telesma and summon the power of an Archangel.

With the use of the cards, the number cards indicate the type of phenomenon which is to occur, while the court cards indicate who or what the phenomenon is to occur to, and store the Telesma which has been gathered.

Out of the suit cards, only the wind-aligned Sword cards have appeared in Toaru Majutsu no Index as of yet, used by Mark Space. Aside from the cards themselves, Leivinia Birdway makes use of the aspects of the four suits with her symbolic weapon, a wooden wand capable of changing forms from a wand to a cup, sword and disc to use elemental magic corresponding to the respective suits.

Suit of Swords
The Suit of Swords represents yellow, the wind, flow and change. It is symbolized by a yellow dagger (黄色の短剣).

Trivia

 * Aleister Crowley's AI, Reading Thoth 78's name is derived from the Thoth Tarot created by him, named after the Egyptian deity Thoth. 78 is the number of all the cards of the Tarot.