Crystals

Crystals (結晶) in Sword Art Online are considered to be one of the most convenient types of items and the closest thing to magic in Aincrad.

Most crystals can be obtained through certain NPC shops, except for the Corridor Crystal. Corridor crystals are the rarest of all crystals, and are only obtainable by trading with other players, or from killing monsters or obtaining them from a treasure chest.

Appearance
Crystals look like eight-sided pillars of various colours.

Usage
They have different uses, namely having immediate effect for recovery, unlike potions, and perform a variety of function outside of healing, extending to teleportation, corridors to locations, and displaying images or replaying voice messages. Though extremely useful, they are expensive, hence making people hesitant to use them, unless they are in very special (dangerous) situation.

Their usage can be prevented by a trap called an anti-crystal field, which became normal for boss fights on the 74th Floor and above.

Known Kinds

 * Antidote Crystal (解毒結晶) (Green) - cure/recover any status effects.
 * Healing Crystal (回復結晶) (Peach Blossom) - completely heals the target.
 * Teleport Crystal (転移結晶) (Blue) - transport the user to a chosen city's Teleport Gate plaza.
 * Corridor Crystal (回廊結晶) (Indigo) - a larger form of teleport crystal that opens a teleport gate to any location that the player has marked. Corridor crystals have a darker shade of blue than the teleport crystal.
 * Message Record Crystal (メッセージ録音クリスタル) (Light Sea Green when recording/playing-back, Teal when inactive) - record what someone has said.
 * Record Crystal (記録結晶) - take in-game screenshots. Can print out via NPC shops later on.
 * Screen-Shot Camera Crystal (スクリーンショット撮影クリスタル) - take in-game screenshots. (color is unknown; assumed to be green) Can print out via NPC shops later on.

Activation
A crystal is activated when the player holds it out and says a voice command specific for the crystal:
 * Healing crystals are activated by saying heal (ヒール) and either aiming it upwards to activate it on oneself or aiming it at someone if the user intends to heal someone else.
 * Teleport crystals are activated by saying Teleport, [Target Location Name] (転移、[Target Location Name])
 * Corridor crystals are activated by saying Corridor open (コリドー・オープン).

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