Gatestones are cut gemstones that are used to trap Eidolons, which are then in turn used to accomplish other tasks. For example, Embergates are used to generate heat or warm and can be used in place of coal or wood in ovens and fireplaces. Frostgates are used in sunward regions of Alesia where ice is not readily available to keep perishables cool. Earthgates are used to reinforce construction in walls and buildings. Skygates can be used to communicate over long distances.
Because the rituals required to coerce and trap an Eidolon inside a gatestone are closely guarded secrets of the Artificers and the widely varied power of the Chosen, Alesians speculate that there is something special about the gatestones that allows them to house the monstrous powers within them. Regardless of their origins, gatestones are readily identifiable by their incandescence. One that is known about gatestones is that the type of gem is important and must be paired with the correct Eidolon in order to function. Skygates are always topaz, Irongates are always hematite, and so on. The size of gatestones are irrelevant, but very few large ones exist. Whether this is due to the quality or clarity of the gem is unknown. Perhaps, because size seems to be inconsequential to the power of the Eidolon trapped, larger gatestones are less common because they are wasteful.
Hematite, emits a soft silver light which makes it hard to distinguish from other hematite; however the lack of a reflection on the surface is a dead giveaway.
Moonstone, in addition to its natural iridescence, Shadowgates appear to draw the light out of the room.
Topaz, Skygates do not emit visible light, but they do create perfect mirrors on their facets when under the open sky.
Sunstone, emits a bright light from the entire stone that closely approximates that of Alesia's sun.
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