A Jitain Gem is the small, shiny mark found in the centre of a Jitai's forehead. When kept as charms, Jitain Gems have the power to alter people's perception of the wearer. This alteration is apparently closer to shapeshifting than to simple illusion; Sudare Singer, for instance, walks on his hind legs when in "human" form, and can force a door with his shoulder, something that would seem difficult for a quadruped such as a tailimin. The transformation appears to be self-sustaining unless expressly called off by the user, and is dependent to some extent on the user's ability and experience-- the Singer twins experienced some difficulty the first time they used theirs, apparently due to holding only a basic image of a human shape in their minds (one which did not include clothes). Inexperienced users may also experience some minor shape aberrations when stressed or taken by surprise. The charms seem to be popular among nonhumans, not all of whom are aware of the gems' origins. It has not been explicitly specified whether a Jitain Gem can be extracted without causing serious harm to the Jitai (possibly because anyone willing to hurt a Jitai to get such a charm would probably have few qualms about killing one anyway) but so far there have been no appearances of Jitai characters without gems on their foreheads.
If a Jitain Gem is separated from its user while a transformation is in effect, the illusion will sustain itself even if the user does not want this; Tulan, for instance, was unable to return to his Kujian form when his charm was stolen by Kade Mito.
In the Jitai-phobic society of the Coyote area, some Jitai have learnt to use their gems to make them appear a little more human in public and avoid unnecessary attention; Zachary Talleyrand and his wife Sparkles both have this ability.