Into...still the Cloud Recesses. A different part of it, though. 

That was strange.  A creature that teleports people a few hundred feet?  Whatever the mirror-snake was, it wasn't supposed to be in the Cloud Recesses.  He starts walking back to where he had been, this time paying more attention to his surroundings.  

It isn't long before he runs into Lan Xichen. Who looks genuinely startled to see him. 

"Jiang-gongxi! You're back?"

"Zewu-jun," he greets with a quick bow.  "Back?

"There was a giant snake with a mirror where its head should be, in the walkways over there.  It sent me to a different part of Cloud Recesses.  Did you see it?"

"What?" 

Jiang Cheng repeats himself, "A giant unnatural snake was over there.  It ...ate? me, with the mirror it had for a face.  I'm uninjured, but wound up a few hundred feet away." 

He's still looking towards the direction of the relevant paths.  It wouldn't be appropriate for him to order Lan Xichen to help investigate.  Perhaps he'd rather have them go warn someone else.  

"Jiang-gongxi, I just came from that direction and would definitely have noticed an enormous snake. You've been gone for several days looking for your brother. Do you not remember?"

"What?  No.  I spoke to you earlier today.

"Wei Wuxian is missing?"

Lan Wangji is going to try to kill Jiang Cheng again.

"Yes. You received a letter from Lotus Pier about it and set off with my brother looking for him." This is a slight oversimplification but one thing at a time. 

"That doesn't make any sense.  He's in Cloud Recesses with us.  Or was about ten minutes ago, when I last saw him.

"I think there might be another time-related thing going on."

"...Wei-gongxi hasn't been here in well over a week; he was expelled for punching Jin Zixuan. Time-related thing?" 

He forces himself to take a deep breath.  Between drawing swords on Lan Wangji and then the giant snake, he's on edge.  

Right.  He remembers Wei Wuxian getting expelled the first time around.  And Lan Xichen doesn't remember their conversation.  Did the snake send him to another version of the unaltered past, later than the first time?  This is going to get confusing.

Well, he'd decided the first time he'd wound up in the past that the best person to tell would be Lan Xichen.  It feels a little hopeless telling him again, though.  For all he knows, he'll be sent somewhere else tomorrow.  

"This might take a while to explain, and need somewhere more private," he says with a grimace.

"Fine. Follow me," he says, leading him to a private office. 

He follows.

They arrive, and he closes the door, putting up a privacy talisman next to--is that a fireproofing charm?

Jiang Cheng is not paying attention to the decor.  He sits down heavily as soon as it would be appropriate, and looks like he wants to rest his head on the table.  

"I am from about eight years in the future.  Various things happened, most of them bad."  He doesn't feel like explaining all of the everything right now.  If this Lan Xichen wants a full report he can ask later.  

"A few days ago, I woke up back on the morning of the salute ceremony in my old body.  I went through the motions more or less as normal.  I quickly realized that Wen Ning remembered the same future events that I did.  Together, we decided that you should be informed.  When we did, you mentioned that Lan Wangji had also experienced this same phenomenon and also told you about it.

"It's only been a few hours since I did that.  

"I think the snake sent me to another point in the original past, so everything before now is what I remember the first time around."

He takes a moment to consider that.  Would Wen Ning and Lan Wangji also have come with him, or is he the only person who now remembers the future.  The future and the not-past?

"That could explain...much. Not long after Wei-gongzi was sent home, Wangji came to me and asked where Wei-gongzi was. When I told him, he asked me how to tell if one was dreaming. Subsequent to that, he behaved very strangely, including actions which were apparently intended as...a more extreme form of advice I gave him related to the dreaming issue. Then you received the letter and Wangji heard about it and left immediately, at which point you came up to me and asked if I thought he knew anything and then left to follow him on the grounds of not having any better leads as to your brother's location." 

That sounds dangerous for that Jiang Cheng, if the Lan Wangji was from the future.  

"Did Lan Wangji seem unusually upset with me?"

He's having a hard time remembering exactly when he currently is.  Eight years is a long time.  Lotus Pier couldn't have been attacked, yet, if he was receiving mail from there.  So much had happened.  One or more people are also acting differently than they did the first time - this might not be something he should remember.  

"...Yes. Do you not get along in the future." 

"We do not."  

"Lovely. Do I want to know why Wangji apparently decided that a priority was plastering fireproofing charms all over the Cloud Recesses?" 

"Yes.  Cloud Recesses is attacked and burned by the Qishan Wen sect."

He wracks his mind, trying to remember exactly when.  It was before they were sent to Indoctrination as hostages.  "Relatively soon, I think."

"They recovered enough from the Xuanwu of Slaughter to attack other sects?"

"The Xuanwu of Slaughter?  We didn't encounter it until after Cloud Recesses burned.  That must be something that someone changed.  What happened?"

"Apparently it was hibernating in a cave in Qishan. The Wens disturbed it and it went on another, smaller rampage before they managed to kill it. Many Wen cultivators died, including Wen Xu. Then its death released some kind of curse, leading to unusually coordinated fierce corpses attacking more Wen cultivators; last I heard, that was still happening."