He was planning to search for the other Angels while trying to find a way to locate the Divine Chalice that he desperately needs, but that plan was out of the window now, as Naela, came to deliver the good news.
Rex was now inside the advanced teleportation formation spot, waiting in silence.
His presence made the guards guarding the area nervous.
I didn't expect Gistella to know about the Divine Chalice. She must've overheard that.
Even though Rex was excited to know Naela had an idea of the Divine Chalice's location, he was then confused—about how Naela knew he was searching for that specific item. After a light pressure, she confessed that Gistella told her about it.
Since he didn't recall telling Gistella about it, she must've overheard it from his conversation.
Rex did ask Flunra about the Divine Chalice.