During the War which first brought her Children to her, thousands of years ago, the Lady of the Stars had continued to search the Lunar Library for information on the origins of the Constellation Senshi, as the Tablets had been found in a tiny room in the basement there. The most she had ever been able to recover were a couple of worn pages hidden in a false panel of the chest in which the relics had had been found. Even then, she knew it had missing pages, and only part of it was legible.
It wasn't the full story, but this is what she has been able to pull together:
The document titled the Brooches as the “Immutable 88”. Immutable meant unchanging, she knew, but she could only guess at the true meaning of why they had been named that. It also appeared that the Tablets' true title was The Binding Chart.
At some point in the past (and it must have been very long ago, as none of the surviving peoples of the Solar system seemed to have a record of it), the tablets had been brought to the Sol system from far away. They were clearly alien in origin.
All of the Constellations were named in a legible section of the document, and matched the labels on the Tablets. Each Tablet were made of alabaster, inlaid with 88 recessed circles of gold, silver, and other precious metals and stones, corresponding to one of the Brooches.
According to the text, there was only one of each of the Brooches, so there could only be one of each Constellation at a time. It now made sense why any pair Constellations like Gemini would need to share, they were reduced to being two parts of one whole (perhaps spirit or soul?). It appeared for a new Constellation to gain power, any others (such as a parent), must first lose theirs. It appeared Constellations could be passed down generationally but this was not the only way.
The Binding Chart had to be activated by a sacrifice... The Lady's blood spreading onto the Tablets must have been why she was able to summon the Constellations without knowing how.
In current times, the Lady found herself worried, both by the fact that the Tablets were called the Binding Chart, and by the power that must have gone into making such a device. Who or what had made it? What was the reason for it (clearly, it appeared to be if nothing else, a method of summoning and keeping an army), and what did that mean for her and her Children... especially given that Cepheus seemed so determined to acquire them? What did he know, and how could she find out? She felt an uneasiness settle into in the pit in her stomach. She needed to know how the Brooches ended up on eighty-eight different planets, and the Tablets here, eventually allowing her to summon the associated Warriors. Why had she herself gained power exponentially as her Children fought those many years ago? Why was she now growing in strength again? The need for answers grow in her mind and she continues to research the situation. Perhaps there will be answers as the Constellations' world expand again.
Related Works:
The Tale of the Constellation Senshi
Technology and Places of the Cloaked World!
The Lady of the Stars and general story belong to nickyflamingo is a collaborative project by all members 
