The immediate problem with the picture of the tenryu above is it doesn't clearly depict Bahamut. We've been led to believe through some interview (idr if it was Famitsu or Reddit) that Bahamut is, in fact, a tenryu-- a son of Midgardsormr (#8).
But Bahamut is said to be one of the first brood! The progenitor of the Meracydian dragons! This does not directly imply he is from Midgardsormr's issue, he could be a grandchild of Midgardsormr or some such.
Dragons in XIV, at least the greater wyrms in particular, have always appeared quasi-deific. They are immortal and possess the ability to warp a mortal's mind. While defectors/dragon sympathizers being heretics is a perfectly understandable idea, there are a few instances in the main scenario which make it clear that eventually those 'touched' by the dragons succumb to madness. This could be explained away as people's sanity breaking down after a thousand years of wars but I think the fact dragons are nigh immortal gives credence to the idea they possess supernatural powers. Also they're fucking dragons.
There's a fucked up draconic hierachy and the only way for-sures we know are:
Dragons (Svara, etc) > Biast > Aevis > Puks. That's right Biast are of a higher social strata in Dravanian society than Aevis, it doesn't seem like it'd be that way since they're more bestial but who knows wtf. There were Peistes in Coerthas known as Wyrmhounds though it's uncertain if they were "wyrmhounds" taught to hunt wyrms by the Ishgardians or "hounds" taught by the wyrms.
Midgardsormr (#8) was far more emaciated in 1.0 as the Keeper of the Lake, it always bothered me his body was much fuller in 2.0, but thinking more on it, that could've been a subtle hint at his regeneration. I'm beginning to think Nidhogg (#1)'s roar was less what woke Midgardsormr so much as the Calamity. Also how fitting the original Mor Dhona 1.0 battle theme was "Phantoms on the Lake" and now we fight Mirage Dragons on the Lake in 2.0. I don't quite understand the Mirage Dragons btw, they're definitely not dragons present at the Battle of Silvertear Skies I think, as we know dragon corpses decay and that'd be 15-20 years. A more likely scenario, imo, is that the Garlean salvagers and Dravanian pilgrims met in battle on the Agrius' ruins and the Garlean gunships succeeding in felling the two dragons. After all Midgardsormr (#8) makes it clear they're dead "ye shall live once more" and what-not. Also, the battlefield is the "Forsworn Promise;" is it we who forswear Hydaelyn's Blessing?
Oh yes, Nidhogg is probably most assuredly #1 thanks to the picture Nama linked. He's missing an eye and we see Estinien and Iceheart before him. Additionally, he looks a lot like the myriad of Dravanians in the Heavensward trailer, leading me to believe these are more accurately Nidhogg's progeny, fighting for their father's cause and what-not. The Dragonsong War, I feel like, will boil down to Nidhogg wanting his eye back; I feel this way because as I stated before even normal dragons possess extreme supernatural / quasi-deific power and are, pretty much, immortal. That is to say, we've never heard of a dragon dying of old age--Midgardsormr lived for millenia, and we know Nidhogg has lived at least one himself. (Fun fact: Assuming each Astral Era lasts roughly as long as the 6th Astral (1.0) and about a decade for each Umbral Era, that makes Midgardsormr ~9100 years old. The great span and magnitude of a dragon's life makes everything feel very fucked up though.
Like, really? Nidhogg has lived for at least a thousand years, roughly twenty years ago he was awake and just razing villages in Coerthas and now he's going to sack the Ishgardian capital? What's changed? Why the sudden upstep in aggression? How the fuck are immortal dragons caught in a stalemate with mortals? The only thing I can think of is that the Ascians have always been involved with Ishgard thus making it a battle of immortals vs immortals or that the Dravanians are beholden to some sort of code to not just fucking wipe out the entire civilization of man. (After all, as long as man is suffered to remain, the dragons will never be at peace.)
We know Ishgard has been at war with Dravania for over a thousand years, but "as long as man is suffered to remain" is a bit awkward as well. The Sharlayans settled IN Dravania, and as far as we know, never had any issues with the dragons whatsoever. Additionally mankind has existed as far back as the Third Astral Era (and in fact, we know Miqote are from Meracydia so it's likely that's how Graha Tia fits into the Allagan bloodline puzzle) So the ancient Meracydian dragons wanted to exterminate all of mankind because Amon and Xande were major dicks, and Dravania seems content with just wiping out Ishgard. Another random point is the only species we know to be somewhat ubiquitous across Eorzea seem to be humanity and dragons.
Could it be the uptick in Dravanian aggression has less to do with Nidhogg (#1) than we think? Perhaps Hræsvelgr (#6) is to blame? (btw various fansites given the celestial dragon artwork from SE state the white & black dragons as Nidhogg and Hræsvelgr so that's where this info comes from) The Norse lore for Hræsvelgr is a bit weird tho; a giant-eagle sounds more like dragon #1 than #6. Additionally the contrast of Nidhogg and Hræsvelgr is pretty cool since one lives "beneath the world tree" and the other at the "northern edge of the heavens" However, in Eorzea, both dragons appear to be located in the Churning Mists (the Sea of Clouds above Dravania). Which is which could be debated excepting the white dragon (#1) seems to be very clearly missing an eye in the close concept art w/ the WoL party meeting him.
Rather, perhaps the legends are wrong? Truth interpreted is truth transformed and all that. Perhaps the dragon Thordan met at the founding of Ishgard was not Nidhogg but Hraesvelgr? Again in the Ishgardian founding myth we have stories told of lesser man being "bewitched" by dragons and taking up arms for them. Another possibility is that Ishgard was not built on Halone's chosen peak-- perhaps instead the great peak in northern Abalathia's Spine is the peak the Ishgardians truly wished to settle. That which is now in the hands of the Dravanians (some people have called the peak "Bahamut's Egg" but I can't find source material for this). Could it be Ishgard the city-state was intended to be a sort of base camp for them to probe deeper and higher into Abalathia, but over the centuries this was slowly forgotten. The highest peak in Eorzea being the true "prize" of the Dragonsong War would be interesting-- as for the Ishgardians being led there by Halone... well... typically when people speak to their gods the Paragons are involved in some fashion, and it would not surprise me here either.
We know Midgardsormr was tasked with protecting the seal on Silvertear Lake (which he actually pretty particularly failed at, let's not forget). Silvertear Lake is, essentially, the heart of all magic in Hydaelyn being the center of the Lifestream/aether--it could be that the highest peak in Eorzea holds a similar importance and that's why the dragons guard it as jealously as they do. Could the return of the Paragons to Ishgard be the reasoning behind the Dravanian's renewed assault on Ishgard.
The Ascians in Ishgard fits pretty canonically too. We finally liberate the Stone Vigil in 2.3 (which has been redoubled by dragons after Isgebind's fall) and the end of 2.3 is when we see the Ascians alongside the Ishgardian archbishop and the beginnings of Lady Iceheart's heretic clan aggression. We all assumed the Ascians were the ones who groomed Iceheart to become Shiva, but what if perhaps she was set in motion by Nidhogg? She quotes Hydaelyn to us (assuming we believe Answers' female vocalist to be Hydaelyn anyways) which is something the agent of the Ascians probably wouldn't do. We also know the dragons and Hydaelyn share some sort of closeness with Midgardsormr's pact. Maybe perhaps then Iceheart becoming Shiva was less Nidhogg's intent than Iceheart's own solution to the problem of Ishgard, but nonetheless Iceheart and Midgardsormr seem less at odds with Hydaelyn than Ishgard.
Perhaps we're all overthinking this a bit and the dire situation Ishgard is in is because of the quickness with which Nidhogg has decided to assault the city. Previously, he slept for about a century between attacks, but this time he's slept much less. Again tho, why? Was it the return of Shiva? Was it Bahamut's dispersal to the aether? Something has woken up Nidhogg early, was it perhaps Hræsvelgr? What of the other tenryu? So many questions still.
Why the fuck were there dragons in Brayflox's Longstop? Why is that our only encounter with dragons outside of Coerthas? Are deathgaze a type of dragon? Actually, looking at Anonymoose's taxonomy work on gamerescape, no deathgaze are not a type of dragon but rather cloudkin.
These are scalekin though, which means they might be able to be considered "dragons" if they possess a degree of consciousness: adamantoise, aevis, croc, dragonfly, drake, eft, gornych, hydra, peiste, puk, raptor, sea dragon, serpent/snake, wyrm, wyvern, ziz. The only ones I have issue with are adamantoise, eft, puk and ziz-- and he has dragons (like XI's shadow dragon) there but I definitely think they're more voidsent.
Anyways, I've sufficiently rehyped myself for another few weeks now and have forgotten where I was going so here's a big list of shit:
Dragons born of the tenryu either begin life similar to their holy parent or grow into a mirror. The natural lifespan of a dragon is over a thousand years and during this time they undergo radical mental and physical changes. I wouldn't be surprised if it's analogous to some sort of pokemon evolution shit lol and dragonflies grow into wyverns into aevis into biast into wyrms into mini-tenryu.
Dragons and humanity likely coexisted peacefully before the rise of the Allagans in Eorzea, Akh Afah Amphitheatre and various ruins shown in teasers contain dragon statues / doors + seating for humans but are pretty "draconic."
The off-the-cuff comment about Yoshida wanting the FMV guy to change the trailer bridge dragon to pink/red instead of white is so when we meet Nidhogg later (who is a larger white version of the dragon) people didn't get confused.
Heavensward story probably like "oh man Nidhogg is attacking Ishgard, go try to stop him" and Alphinaud qqing and like "let's try for peace" and then Iceheart is like "mankind can never be at peace with dragons as long as Ishgard has Nidhogg's eye" and something like Nidhogg having 2 eyes is actually more beneficial to Hydaelyn and Hræsvelgr is using Nidhogg's partial blindness to fan the flames of war between mortal and immortal and Hræsvelgr just wants to subjugate the world and have dragons rule as the rightful kings of the world and Nidhogg keeps him in check but he needs 2 eyes and now Hræsvelgr has woken up again and this is the first time Hræsvelgr woke up w/ Nidhogg missing an eye and he's capitalizing on it somehow. Then after we resolve the conflict between Nidhogg, Hræsvelgr and Ishgard, the other 5 tenryu wake up and are pissy pants (3.x+) and we begin to unravel the Ascian involvement even further (while dealing with their primal shenanigans during 3.0) and then the Dravanians summon Shinryu (their primal in like 3.4+) and the Monetarists try to like rent Omega out to Ishgard to fight Shinryu so we have to end up stealing/fighting Omega and then Shinryu.
I really lost track of myself, but anyways the Scions prob aren't dead either, but Nanamo prob is and Raubahn is prob gonna escape Marajasa Pit at the last possible moment to save Ul'dah and our asses. Urianger might get corrupted or begin to see the Ascian's point of view, but I find this unlikely. The Isle of Val will probably be confirmed to be sent to the Void and that'll be our 24-man since it was confirmed the FF6 Floating Allagan Continent wouldn't be a raid. Alexander is probably what's draining the world's aether atm and was probably summoned by the Illuminati into a derelict Allagan warmachine (another thing made to house a primal's essence) and we have to go in and deactivate it by fighting off automated Allagan defense systems and shit.
The end.