[Rose is not usually a person one would call "helpful" and she usually doesn't care to share information. But, given the situation they're in, it's worth it to be proactive. Especially since she has some very important information to share.]

I spoke with Forneus before our fight with Dvalin. According to him, we aren't the first group of travelers who have come to Teyvat. The other two were siblings killed by Celestia.