Athena looked thoughtful for a moment, then said "You know, out of the three of us, you're the most important, Jon. If someone used the stone to make you disappear, maybe that would make the stone disappear too, since you were the one who inherited it. That could also, logically, return Zoe from wherever she went too, but it could also make things worse. We need to make sure that you always stay here."
"But how? Without the stone, I can't ..."
"With this," Athena said, interrupting him. She gestured towards her pendant necklace. "If you wear it, none of the changes in reality will affect you."
"But what about you? Don't you need it?" Jon asked.
"Right now, you're more important. Once we find the stone, we can try to fix things later."
Jon thought about it, then decided to ...