Astral Amulet (Origin of)
What is the nature of the Astral Amulet, which consists of a piece of wood in a purple pouch with the Zeal crest on top?
Magus's Amulet and the Astral Amulet may be one and the same. Magus's Amulet came from Schala; she gave it to him before the Ocean Palace Incident, and he kept it throughout his life. Meanwhile, the Astral Amulet is a mysterious artifact from Zeal possessed by Lucca and given to Kid during her infancy. It consists of a piece of wood tucked in a purple pouch bearing the Zeal crest in gold and black. Now, consider that Cross's backstory was probably fleshed out before they decided to axe Guile's backstory as Magus. Is it perhaps plausible that Magus's amulet is the Astral Amulet, and that Magus, having knowledge of Project Kid or simply of Kid's existence, visited Lucca and gave Kid the amulet for her own safety. This possibility would not only explain the mysterious origins of the Astral Amulet, including its crest bearing the Zeal emblem, but would also neatly link the mysterious item with established Chrono canon. Thematically, it is also interesting to see Magus give the Amulet back to his sister (albeit in a different form). Lucca's speaking to him as the very personal Janus may imply that they became closer friends (and that the letter was written much later after 1004 A.D., which would be likely since she had to have had met Luccia by its writing).
The main issue with this theory is that the two items look nothing alike. For them to be the same item, the assumption that the concept art changed would have to be made. While the appearances of the Hero's Medal and Time Egg were changed between Chrono Trigger and Chrono Cross, it is difficult to simply write this off as a change itself. Another problem is in that Magus's Amulet is depicted as being worn around his hip, which precludes the possibility of the amulet being a small item that could be concealed on one's person.
From: Theory (Objects)