Notification Crystals are portable crystals held by the people of the Empire, one each. Notification Crystals can be any gemstone, so long as not the same as other's so long as either character are somewhat important in the story. Such gemstones include Auurin Cennire's Pyrite crystal and Shojohi Yoshima's Amethyst crystal.
Notification Crystals are all powered by the large tree-like structure of Najek Crystals in the guarded center underground of the capital, Crystal Valley . Notification Crystals themselves are also slightly genetically engineered to be part Najek, which is how they have any power at all.
Some Notification Crystals can be liquids and gasses at room temperature, however, these are incredibly rare. The same crystals also can be modified very much, especially when situated in Kika-Muki , the place Notification crystals were developed.