Celestial Sphere of Trysts is one of the magical items described in Monster Girl Encyclopedia World Guide III: Sabbath Grimoire.
Guide Book Entry
A huge hemispherical slate. A pattern is engraved on the surface, and if you look closely it is a map of surrounding continents and islands. By touching the hemisphere the magical tool begins to move, and if you say the name of a species in this state, every location that species is located will begin to shine faintly. However, the scale is extremely small, because it is a map that can only distinguish the contour of continents and islands, the position can only be specified to the extent of somewhere on this island or the middle of a continent, you cannot determine exactly where they are in a town or forest, nor things like the number etc.
In this Celestial Sphere you can locate not only mamono, but humans, animals, angels and the like are also included. The name of the species needs to be said exactly, and if it is wrong the Celestial Sphere will not react. Also, "Mamono" is not a race name, it is a generic name of various species, so specific races like "Lamia" or "Succubus" need to be said.
Although just a section, it has the power to see the world and project that information, and it is one of the magical tools that gathers magical skill and sophisticated wisdom. And yet, this is also a great big "dud". A high-ranking magic expert mamono at the heart of Sabbath and a skilled artisan gathered to develop this magical tool, with the intent of allowing all mamono to easily obtain a partner, a shared wish of all mamono. However, because the extent of its effect is too large, detected magical power cannot be distinguished in detail, not to mention searching for indviduals and specifiying by gender cannot be done. Moreover, by declaring the species "Human", because they exist throughout the world, almost the whole hemisphere shines, and so it became useless.
Nonetheless, you can examine the rough distribution of specific mamono species, you can know the places where angelic beings such as "Angels" and "Valkyies" are staying, and you can also examine the rough location of races with very small populations. Gentlemen thinking about wanting to marry a race with extremely few indivduals such as "Dragon", by all means why not attempt it? Although I should say, this hemisphere exists only in places such as Sabbath's base and the sorcery institutions of nations that have become Mamono Realms. Other than that, there could be a small fraction left behind around abandoned research facilities.