I'm sorry I can't write anything serious atm since I'm working on my cynonari fic, but generally:
The ones coming after Sethos are Pantalone's men.
Dottore left notes about a backup plan, something about the 'rite of resurrection' (yes, Qiqi's C6).
Qiqi's severed soul was resurrected by the angel Zibai using adeptal arts. More in-depth studies of this practice were conducted along history, and the temple of silence happens to possess much of the documentation, including parts that go against Ronova's rules and are therefore considered forbidden knowledge.
Very understandably Pantalone wants this and will not hesitate to kill Sethos and everyone in his vicinity.
They're lucky the first time the Fatui come to scan the area, Wanderer happened to be there accompanying Durin. Since Sethos learned Durin struggles a little to control abyssal energy overflows, he thought to refer him to a few articles on the topic, and Wanderer naturally joined.
They were taking a break playing catch in the oasis outside when they spotted troopers coming their way, though they seemed lost.
Sethos wanted to just go inside and let the temple do its thing with the camouflage, but Wanderer thought that'd make them sitting ducks if the troopers had any type of scan tech on them.
As such, Wanderer took it upon himself to initiate a sandstorm with his anemo vision, just strong enough to wipe the entire envoy out. He then personally dragged each and every one of them a few kilometers away just to throw them off, cursing from the effort the entire time.
Over the next few weeks, he finds that he cannot calm down about it. Has to figure out if they were there coincidentally or if they were looking for the temple specifically.
So Wanderer does something he thought he would never ever do: he goes to an old contact he knew from his fatui days -set aside that the man doesn't remember him anymore- and uses all the correct code phrases to convince the other he's fatui before asking for the mission details.
Learning not only that Pantalone was looking for materials on resurrection but also for Sethos personally, Wanderer high key loses his shit
He can't really tell Sethos about his past. To Sethos, he's simply 'hat guy'. As such, he can't explain how he got the info or the level of threat either... but if he doesn't protect him, Sethos will die and Dottore is likely to be resurrected, which, absolutely fucking not on his watch
He can't even explain to Sethos why he wants to go everywhere together suddenly and bodyguard him, so he starts to kinda... stalk him. Just a little bit.
Sethos is far too sharp to be casually stalked. He knows he's there, mostly. Calls him out or plays tricks on him. Doesn't fully understand why Wanderer is like this, but...
When Sethos finally vents avout it to Cyno and Tighnari, they both get weirded out, Cyno points that it's harassment, but Sethos does not view it that way at all and refuses to file a complaint. If anything, the conversation convinces him that Wanderer might... like him. He likes him too, this is awesome news to him.
Que aggressive flirting, Sethos making them both lunch even though Wanderer doesn't have to eat because he knows he will be there.
Highly flustered Wanderer alternating between acting as Sethos' personal one-man swat team and getting hit on
And like, objectively Sethos is attractive. Everyone thinks so, right? It's not just wanderer. It's not weird for him to get flustered, alright? Anyone would get butterflies in this scenario. Shut up.
At times Wanderer resorts to cancelling a whole fatui mission using their own codes, like "Boss can't come today, he got caught up washing the dishes, new orders say we can spend the day sunbaithing until the north winds pass." When the lingo changes he's left with no choice but to kidnap and torture fatui officers for new codes.
Doesn't take long before Pantalone figures out there's a traitor however he cannot figure out who it is, considering they seem to know the organisation as well as a harbinger.
Unfortunately the missing harbinger is something he and Dottore hadn't discussed in depth, so even though Dottore cracked it already before his death, Pantalone takes a while longer to come to the same conclusion.
Seeing the severity of the threat, Traveller gets involved. They defeat Pantalone in the upcoming snezhnaya arc and he dies :(
Sethos takes part in the battle, gets injured but it's nothing crazy, bothers Wanderer more than it does Sethos.
Since Irminsul was burnt, the rules determining nobody can learn of Wanderer's full identity are null. Sethos learned the truth at some point during the fighting.
Sethos even knew of wanderer as kabukimono in the temple's inazuma collections, and read some corrupted books about the 6th harbinger's deeds, but never considered both might be hat guy.
He's conflicted, but then Wanderer comes over to check on him and he realizes his feelings didn't change and this is the same hat guy, only with a name.
They get together, you know the drill. Kisses and love confessions, realizing they understand each other on a deeper level than anyone else can, etc etc
