A magical crystal that can be found in the soil of the Mamono Realms and appears in the Monster Girl Encyclopedia World Guide II: Mamono Realm Traveller's Guide book.
Guide Book Entry[edit]
One of the unique ores that can be mined underground in any mamono realm, they're even easier to imbue with magical energy than Mamono Realm Silver. Not only are they used as ornaments, the gems are also excellent as a material for magic items. The raw gems are transparent and colorless, but if imbued with essence or mamono mana, the color, brilliance, transparency and even shape of the crystals will variously change depending on the owner of the essence or mamono mana that's contained inside.
These changes are different depending on each individual, and one person’s energy cannot make exactly the same gem as another person. A gem is thus produced that is “unique to each person” and can only be made with that person's essence or mamono mana. For that reason it's even possible to distinguish an individual through these gems.
Furthermore, once a gem has had essence or mamono mana poured into it, it stores that energy and this causes it to become fixed. This means that once a magic gem has been changed, it won't ever change again. Since if it is accidentally imbued with magical energy and changed a magic gem cannot be returned to its original state, excavated magic gems need to be handled carefully.
They are also difficult to handle when processing, so only an artisan with excellent skills can be entrusted with it. Additionally, when infusing magical energy into a magic gem, the gem must be of high quality and purity to match the strength of the energy. If the quality of the gem is unsuitable for the greatness of the magical energy, then it won't be able to take it when the energy is poured inside, and it will shatter. For that reason, magic gems of more powerful individuals are regarded as more valuable. Notably, it seems that there still aren't any gems in existence that can contain the magical energy of the Mamono Lord or her husband. Because of the richness of their brilliance, there are passionate collectors of magic gems among both humans and monsters.
Regardless of whether it's the mamono realm or the human realm, magic gems that are infused with the essence or mamono mana of particularly well known people are precious and wildly popular. Such famous people include leader-class monsters of the Mamono Lord's army, or fallen former heroes; as well as current heroes of the Order, and the popes and saints of religious states.
Engagement Rings[edit]
Engagement rings are rings that are exchanged at the time of marriage. Originally, monsters had no such tradition, it was a human tradition, but monsters have also come to practice it through the faith of the goddess of love. When a monster couple exchanges engagement rings, these magic gems are often used. The bride and groom will imbue their mamono mana and essence respectively in the magic gems of the two rings and exchange them with each other. The bride will put on the ring of the groom's color, and the groom will put on the ring of the bride's color.
Engagement rings are not necessary for marriage, but even a monster with no interest in jewels will change her tune if it's something that contains the essence of her beloved husband. She'd be very pleased to have proof of the love she shares with her husband, and she'd continue to treasure it. A ring infused with the essence of her husband can make a monster feel like she's always with him whenever she's wearing it.
Furthermore, the color and brilliance of magic gems varies depending on the individual. It would be extremely rare, but it's probably even possible for them to change into mere stones that are poor in color and lack brilliance. However, that sort of thing doesn't matter to monsters. As far as monsters are concerned, what's even more important than the fact that it's a jewel, is the fact that it's a stone containing their husband's essence.[1][2]