So most of the shadowflame shard stuff seems to imply that this is like the combined conscience of several distinct beings- those being the elves Saeryn and Rhyas, Everblight, and Cyriss.
Mostly they just seem like they’re trying to guard Caen from…some unknown threat.
It never really says very much but that it is from “beyond the gate”.
That depends on who you are:
Are you a khymaera: they are the gleaming snakeman thar will save the day.
Are you not a khymaera: They are the borg and seek to kill and assimilate you
Welll i don’t know if they’re just going to attack everyone. They seem to have a lot of memories of the nyss implanted in them, particularly of a fairly isolated nyss clan. they even still refer to themselves as a shard. so they may in many ways have the traditions, etc of the nyss. they may attack a place, perhaps because it has offended some bizarre tradition of them, only to leave another nearby village untouched. They also can follow an enigmatic doctrine of cyriss, acting strategically and logically. So they might be more inclined to be like a very mechanically minded elf, if that makes sense.
I’m tickled by the idea that the threat they’re trying to plan for is actually something that only a goddess who thinks in epochal timescales would worry about.
Like Saeryn and Rhyas are freaking out thinking they gotta be ready for something and Cyriss is just off in space thinking “I sure hope they got my message, they’ve only got a few million years before their sun goes supernova. “
Well, unless whatever is coming up in Warcaster shows up in Warmachine first 
Now I gotta find time to read. Kind of more excited now, can’t lie.
Maybe the great threat that’s being referred to is the Fellgoeth?
Also, emergence part 2 dropped!
I’m betting it’s relevant to the vision Blighterghast shared with kreuger
I was totally wondering the same thing! Part of me
Wonders is Saeryn has mislead the entire collective into feeling this sense of purpose as a way to control things that also believe they are sentient (Rhyas included). It almost feels a little like seasons 1 and 2 of Westworld; all the robot hosts are trying to get to somewhere (a promised land, a happy ever after), but that somewhere didn’t actually exist. It was just a drive/motivation with no real target.
But counterpoint, in some of the Warcaster Neomekanica fluff they’ve implied that there’s some great devouring enemy on the edge of the Cyris galaxy, and that eventually it’s coming back. Maybe that’s the same dread that Saeryn has foretold, and it will eventually come for Caine.
Or, third option, it’s climate change. Gotta turn all these warjacks into snake people if you’re gonna keep temperatures within 2 degrees Celsius of AR200 levels.
In the new Khymaera lore, it’s definitely hinted at that the Cyriss influence was always intended to clear out dragon consciousness, and I’m almost certain that’s a tie-in to whatever the Exiles in wnm end up being