Crystals

Crystals are special items that can perform a certain effect. So far, four variations of crystals have been shown in the series of SAO.
 * Teleport Crystal: Blue coloration. User vocally speaks the phrase "teleport" and the location of any settlement on the floors explored in Aincrad; player is transported there instantly.Crystal.jpg
 * Healing Crystal: Red coloration. User vocally speaks the phrase "heal" and all HP lost is regained in a second.
 * Antidote Crystal: Green coloration. User vocally speaks the phrase "cure" and all effects of paralysis, poison, and other hindering restraints are removed.
 * Boost Crystal: Yellow coloration. User vocally speaks the phrase "boost" or "upgrade" and a specific skill, by the user's choosing, will be temporarily enhanced. Effect only lasts thirty seconds per crystal, and only one crystal may be active at any time when boosting a skill.

Teleport Crystal (Blue)
The blue crystal is known as a Teleport Crystal. With it, a player need only to say the name of the location that they wish to travel to, and he/she will be able to instantly travel there.

While the crystal may allow for instantaneous travel, exceptions to using the crystal apply in certain locations and circumstances.

Exceptions

 * Boss Rooms
 * Non-populated settlements (Must travel to a town or village)
 * Unexplored floors of Aincrad

Healing Crystal (Red)
The red crystal is the Healing Crystal. It is useful when a player's health is extremely low during a big fight and health vials are not capable of replenishing the health fast enough. The amount of health regained does not vary between levels. Players with higher levels will regain all of their health with a single crystal used.

Antidote Crystal (Green)
The green crystal is the Antidote Crystal. Players that are affected by hindering restrictions (paralysis, poison, etc...) are instantly taken away. However, only one crystal can take away one affect at a time.

Boost Crystal (Yellow)
The yellow crystal is the Boost Crystal; able to instantly boost the stats of a desired skill that the user decides. The time duration that the skill is boosted is thirty seconds. Only one boost crystal may be used on any one skill. Up to three skills may be boosted at any time.