Dragon Tear (Origin)
What was the origin and original purpose of the Dragon Tear? We know it was used in rituals at Fort Dragonia, and the game clearly states that it's a legendary artifact capable of allowing body switching. But was this its original purpose? Doing so seems to have shattered it, implying it had some other, lesser purpose.
The area housing the Dragon Tear in Fort Dragonia had murals depicting evolution. Perhaps the Dragon Tear was created as a tool to aid evolution of the Dragonian species. It's possible the Reptites crafted it (from magic or otherwise) and were able to evolve to Dragonians this way.
Then again, the mural depicts the corruption of humans by Lavos, not self-directed evolution of Dragonians...
The Dragonians may have created them as powerful healing artifacts. Since they're capable of reconstructing bodies (in reality, reshaping the users to "switch" bodies, instead of actually switching their minds), they should be capable of wondrous healing powers as well, whether reconstructing lost limbs or perhaps removing malignant cancer or tumors. The only drawback to this theory is that the Dragonians went extinct, implying they couldn't live forever or heal themselves perpetually. Then again, the Dragonians gave the Dragon Tear to the people of El Nido as a gift, so perhaps it wasn't in regular use.
A quote from Direa:
Its power is unknown, yet much too powerful for any human. If the ruin were to be activated by chance, it would emit uncontrollable power...
Imagine if it were actually a weapon, healing its user for the purpose of combat!
Of course, Belthasar's machinations must always be taken into account. Whatever happened, the Dragon Tear was ultimately meant to be a part of Serge's journey and produce the Tears of Love and Hate to create the Chrono Cross. It's possible the Dragonians were just acting as stewards for the Dragon Tear, knowing it would be used for something important later on—something related to Lavos and the Time Devourer, thus the murals in Fort Dragonia depicting Lavos.
From: Theory (Objects)