Some posts on weibo were throwing this out there based on hints given by the production crew and it makes sense to me. If it turns out to be true and they execute it well, then we're in for a treat.

The theory is that Chukong and XY are actually stuck in a fate cycle where the current one (the heavenly realm) is where Chukong break them free. Below are some hints that suggest this.

- If you watch Episode 1 at 26:00-27:30 minute mark, XY lied and said Chukong seemed familiar and his expression immediately changed, then got close and said "I finally found you, Xiangyun." His tone sounds like he was speaking as Lu Changkong somehow?

- There was mentions that 2 versions of the "Bloody Wedding" was filmed. The one we saw in Episode 12 was inside, where LCK was kneeling when XY came to him with the dagger on her throat, but there were photos posted by the team on weibo showing the same scene, shot outside and SXY was holding a sword instead of the dagger.

- Then this trailer flashed a shot at 1:59 briefly showing a reincarnation that wasn't in any of the listed incarnations. Could this be another version of LCK(looks like his clothes) and SXY where they get their happy ending?
https://youtu.be/GelE7HiRF_c

- The lyrics of the opening OST tells so much about the plot.
https://youtu.be/hrbpkRvMUYk

It's also a part of the photos below where the production shared countdowns to airing date, but the numbers on each maybe strategically hinting at the order of each incarnation. They didn't count the boar x tiger one here.

There were a couple more hints, but I couldn't make as much sense of them so will exclude them for now. 

Below are the reincarnations order that the official weibo has been posting a few times.

Caption:
Divine Chu Kong - Single for 30,000 years
Fairy Xiangyun - Has worked for 3,000 years
"Marriage fairy promotion story. Single god of war experiences love."


Caption:
"Fairy fell into the world and turns into a footman. The "God of War" heroic name is about to die." (I think this was the boar x tiger life, but they wanted to keep the graphics a surprise)


Caption: (to note: they split up the idiom "qing mei(her) zhu ma(him) - childhood sweethearts" into 2 and inserted them next to their names. I'm leaving the pinyin so the whole text makes sense)
Song Xiangyun - Clingy "zhu ma"
Lu Changkong - "Qing Mei" waits for me
"Story of raising a golden 'zhu ma'.  Story of a lovable husband general chasing his wife."


Caption:
Chu Kong - One heart for one person
Yang Xiaoxiang - One heart for master
"Master and I have a heart to heart.  Predestined woman wait for me."


Caption:
General Chu Kong - Operating system Xiangyun
Princess Xiangyun - Actually Chu Kong
"General husband and I changed bodies! Pampered princess is actually me?"


Caption:
Chu Kong - Prince in love
Cang Hai - The Empress chasing her lover
"Domineering empress forces love. Got on the wrong wedding carriage, found the right person (in smaller font 'son-in-law returns'"


Caption:
Cat Demon Chukong - Domination king
Tiger Spirit Xiangyun - Bravely entering the sly world
"The cute tiger seeks to be loved. The white-haired demon king swears off love"

Tiger and pig you didn't mention 

 Muskan Gupta:

Tiger and pig you didn't mention 

It's there, the poster with only a "?" on it. Productions didn't want to reveal the graphics before it aired, but the caption definitely referred to them.

 Lan_Lan:
Chu Kong - Prince in love
Cang Hai - The Empress chasing her lover

cang hai? did they really write that on a poster?!

 Perfectlyflawed:

cang hai? did they really write that on a poster?!

Yes, they did.

Holy smokes! I was just thinking about the bloody wedding having a different version with the BTS videos and all.  Thanks for sharing this Lan_Lan! If this is true then oh my goodness! I'm locking in my seat belt and  staying for the full ride.  It makes a lot of sense. 

Very interesting theory! do you think that maybe the ML is only pretending to have lost his memory and actually wants to finish the cycle and possibly save the FL..... It would be really interesting because it would go against the "cold ML who denies to feel anything for the FL" trope - it would show that he actually knows more than he shows and is very careful not to show any care in front of this sketchy brother.....it would add more layers into their early interactions....

 RouteVenus:

Very interesting theory! do you think that maybe the ML is only pretending to have lost his memory and actually wants to finish the cycle and possibly save the FL..... It would be really interesting because it would go against the "cold ML who denies to feel anything for the FL" trope - it would show that he actually knows more than he shows and is very careful not to show any care in front of this sketchy brother.....it would add more layers into their early interactions....

It's possible, otherwise why would he say that line in episode one. I hope that's the way it plays out.

 Lan_Lan:

It's possible, otherwise why would he say that line in episode one. I hope that's the way it plays out.

Agreed! And maybe in the flashback with Xiu Ming and Heavenly Emperor, it would be cool if it turned out that Chu Kong only pretended to be unconscious. Because, otherwise, why would he be there? It seems it wasn't necessary for him to be actually shown there for that dialogue to work...

i dont know how to quote long post but i dont think the one from the trailer at 1:59 is lu changkong and song xiangyun's happy ending but their last mortal incarnation (if you look closely, xiang yun's hairstyle is very similar to the one we saw at 1:39) and the same picture was also used at the very end of the end credit. also we'd also see snippets of that lifetime (from the poster marked as 7) in the trailer and mvs for the ost.

https://youtu.be/PzaQB1ymjIY

i dont understand much mandarin but at 1:55 in the mv, (it's the same scene as 1:59 in the trailer)  she asked 'this time who are you here as' but i dont understand his reply

in the novel it's the lifetime where xiangyun became chu kong's master and tried to convince him to cultivate to become an immortal (but not sure how they'd tell this part bcs the drama is much different from the novel but maybe it'll be the lifetiem that'll break the fate loop)

 Bored Kitty:

i dont know how to quote long post but i dont think the one from the trailer at 1:59 is lu changkong and song xiangyun's happy ending but their last mortal incarnation (if you look closely, xiang yun's hairstyle is very similar to the one we saw at 1:39) and the same picture was also used at the very end of the end credit. also we'd also see snippets of that lifetime (from the poster marked as 7) in the trailer and mvs for the ost.

https://youtu.be/PzaQB1ymjIY

i dont understand much mandarin but at 1:55 in the mv, (it's the same scene as 1:59 in the trailer)  she asked 'this time who are you here as' but i dont understand his reply

in the novel it's the lifetime where xiangyun became chu kong's master and tried to convince him to cultivate to become an immortal (but not sure how they'd tell this part bcs the drama is much different from the novel but maybe it'll be the lifetiem that'll break the fate loop)

Yeah it's not as LCK and SXY but their final incarnation as all parts of themselves I guess. He said "Regardless of now, or 30,000 years ago. I'm destined to find you." I think the 5th life will have the her being his master plot since I remember they have another sword dancing scene. We'll just have to wait and see, but it'll be interesting to see how they pull it off.

that makes sense but i thought this was the same incarnation as the sword dancing one? idk anymore lol.

 Bored Kitty:

that makes sense but i thought this was the same incarnation as the sword dancing one? idk anymore lol.

I was connecting it based on their hairstyle, but everything is so scrambled so we can’t be sure. I’m still trying to find clues that he currently knows she’s CH, otherwise why would he say that in ep 1 when he first saw her? But in the latest episode he was talking to XM like maybe he doesn’t know, so now I don’t know anymore haha. Maybe he’s pretending because he doesn’t want the emperor to find out he remembers what happened. The way he asked XM to tell him if he knows what happened 30,000 years ago so CH can be proven innocent had like a desperation to it in his eyes. 

 Lan_Lan:

I was connecting it based on their hairstyle, but everything is so scrambled so we can’t be sure. I’m still trying to find clues that he currently knows she’s CH, otherwise why would he say that in ep 1 when he first saw her? But in the latest episode he was talking to XM like maybe he doesn’t know, so now I don’t know anymore haha. Maybe he’s pretending because he doesn’t want the emperor to find out he remembers what happened. The way he asked XM to tell him if he knows what happened 30,000 years ago so CH can be proven innocent had like a desperation to it in his eyes. 

same lol. this is my thought after watching ep 22: since chu kong couldn't do the soul protection thingy, i think he may already did it 30k yrs ago or if this is a fate loop like we think, then it's possible that he also left a part of his consciousness into the fate cycle as well like immortal li leaving clues for them in the mortal realm. 

so maybe, that consciousness only comes and goes and he need to keep finding the answer during the fate loop to break it and obtain all his memory (maybe it's something that got to do with the mirror in the ost mvs)? idk if i'm making sense anymore lol.

but he does seems desperate to make sure xiangyun is not harmed. i dont remember from which episode (around ep 19 to 21) but he stressed that he will make sure that xiangyun is not sacrificed again for the whole realm, which is weird if he was only talking about their primordial spirit feeding one another (bcs in its essence it involved only the both of them) bcs to his knowledge it's only happened once

Yes, I caught that too! It's in ep. 20 when he said he won't let that happen again and that triggered another hint for me. I did question myself afterwards that maybe he meant her dying in the 2nd tribulation, but you're right, XM did say the whole realm so I do think he meant 30,000 years ago.

I think maybe the soul protection spell casting happened during their "wedding" because that's when CH was "killed" since CK was wearing the red wedding outfit in the flashback between the emperor and XM. So when the emperor erased his memory, maybe he only managed to erase from that moment up to when she died and CK fell asleep. It's possible that parts of his memories were scattered into the fate cycle and the tribulations are how he regains all his memory as you say. 

If the same events as the first two tribulations happen again in this fourth one, ie. failed assassination attempt, romance novels, giving hairpin, etc... then we can continue thinking it's a loop. If not then we can throw that out, but I do think it has something to do with time and going back in the past to correct the future. So maybe the current heaven realm is essentially the first lifetime that CK has to redo with a positive end to correct the "future" one when CH died? Now I might not make sense haha

This drama is being very subtle with their hints instead of beating you on the head with it, which is what I love.