If this Typhlosion does NOT have Focus Blast or a legit strong Fighting move, then this raid is going to be a relative cakewalk for several good pokemon. I just can't imagine a 7* Ghost Boss with a big signature Ghost move that just lets a bunch of good Normal and Dark types in the dex waltz in and run train on it. Now, what GF might do, because they've done suboptimal stuff in the past, is give it a physical fighting move like Low Kick or Brick Break. But whatever the case, it's hard for me to imagine that GF is going to put Hisuan Typhlosion out there to be fodder for the right Dark types and Normal types to pound on it and coast along without fear of any serious damage. However, if Typhlosion has a decent Fighting move, then this 7* raid will be more of a challenge.
At this point I'm not too interested in looking for or reading about "good support mons" for this raid. I think there will be plenty of them, if you are looking just to give general support to a team. Posting yet another mon that can generally survive, do cheers, put up screens, maybe do some healing, yada yada yada -- that's all well and good, but I don't think it will be some brilliant insight that is going to "solve" this raid. I might be wrong, and we're gonna be in short supply of support mons, but it feels like we'll have a good amount of generic support mons based on what Typhlosion can do, barring any crazy stuff GF might do to knock us on our ass (which they certainly do often).
What I am searching for is something that can stand in there and beat down Typhlosion with big hard hits and actually clear the raid. Assuming Typhlosion gets Infernal Parade, Big Fire Move, and Focus Blast/Fighting Move -- the list of mons that can actually do damage in big chunks without dying quickly just got a lot shorter.
And, I'm also not looking for whatever Arceus set is going to be workable in this raid. Again, it's not terribly brilliant to discover that a pokemon that has 120 base stats across the board, that can be any one of the 18 types in the game including any one that hits the boss SE and is not weak to the boss stabs, and it has the biggest movepool in the dex with access to every TM in the game -- wow, you're not gonna believe it, but that pokemon can be built to be good for a Tera raid! Yeah, uh, it's literally the God pokemon and so it's probably not gonna suck in any raid if you build the right one. Posting Arceus sets is fine, if there is some new twist you have found that isn't obvious. But if you're just gonna post yet another Arceus that has the fill-in-the-blank requisite typing, with a moveset consisting of the bog-standard SE Offensive Move, Boosting Move/Debuff, and Recover -- it's usually not very enlightening IMO.
(BTW, my comments about Arceus are NOT directed at Vengeance because of the set just posted above. I'm just talking in general about Arceus sets frequently posted in these raid threads)
I don't have any magic answers for this raid, but here's a interesting mon that I have had raised to lvl 100 in my boxes for a long time, and rarely get to use it for Tera raids, that actually might be useful against Tera Fire Hisuan Typhlosion if I tweak the build a little:
Glimmora @ Shell Bell
Tera Type: Rock
Calm Nature
EVs: 252 HP / 180 SpDef / 76 Speed
- Power Gem
- Acid Spray
- Light Screen
- Sandstorm
As I said, this isn't a magic answer, but Glimmora ticks a few boxes that other mons can't. The biggest thing is that it is a Rock type, so it resists Fire and hits it SE, and it's a Rock type that isn't weak to Focus Blast. It's a special attacker, so it's not going to care as much about burns, which seem likely to be a central feature of this Typhlosion raid. It gets access to Acid Spray (stab at that, not that it matters a lot) which is a much preferred way to "boost" in tera raids, since you can build tera at the same time. And being a Rock type means that if it sets Sandstorm (probably only in solo runs, because otherwise you screw your neighbors) it gets a boost to SpDef, and even better is that the boost can't be wiped by the raid boss. Light Screen piles on top of all the other defensive build elements to give Glimmora maximum survivability while Acid Spraying and then getting back lots of health from the Shell Bell. The Speed EV's are to get Glimmora to 227 speed and outspeed neutral Typhlosion.
Glimmora has problems, which is why it languishes in my boxes for most raids. But maybe on this raid it can fill a niche as one of perhaps few offensive tools we can use somewhat reliably to take down Typhlosion. We'll see!
(Or Rock if you don't want Judgment weakened assuming he's packing Sunny Day, but that'll just leave you more vulnerable to Focus Blast)
