I think I found out how, you have to first finish the green gem quest belonging to the temple of lizards & take it with you. Then when you go sleep, you'll meet that mysterious existence who's always after the gem, I gave it to him but you could try other options and then when you go back to the ruins again and tell them the news, they'll "celebrate" I think at a waterfall. Sorry for long post but it's a long chain quest lol, hope this helped a bit