Since its Dungeon and Dragons game. What creatures would be more classic as dragons? And for Baldur's gate in particular, there are two legendary dragon that dwell in vicinity.
Both came from "Wyrm's of the North" columns, that was written by Ed Greenwood himself.
Miirym:
Once a silver dragon, dwelled near Candle Keep, and accidently killed few scholars and destroyed few precious tomes.
Sentent to be a guardian of Candlekeep for 20 years by arch-sorcerer. Unfortunately for here sorcerer died in 15 years, never releasing her from her sentence.
She dies later, but remained to be a guardian as a ghost.
Nowadays she dwell in cellars under Candlekeep, guarding it from any unwelcome guests from Underdark.
Mostly she is still a good character, though somewhat gloomy and cynical.
Candlekeep itself is iconic place in BG series, as in where original trilogy starts. And if we ever would visit Candlekeep in BG3 - Miirym would be an amazing character to meet.
She is depicted merely as a pair of ghostly jaws, so for ppl who don't know her - she wouldn't even be recognisable as a dragon. Stats-wise there is no creature that represent her as a been well in 5e. Still, it's worth trying port something from older editions.
In any case, would player be stupid to attack her. Fight obviously should not be trivial.
Otherwise she very much could be an interesting NPC to talk to. Telling great many things about Candlekeep, and possibly even about her own tragic story from from first-person perspective.
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Klauth:
![[Linked Image]](https://static.wikia.nocookie.net/forgottenrealms/images/d/d9/Klauth.jpg)
Quite possibly the most powerful dragon that still lives. And very-very old.
He is actually very well known among baldurians. With quite a few sayings expressions common among population, such as:
"Don't go near him early of mornings; he's apt to be a right Klauth until he's had a mug or two."
"Blood and bodies everywhere . . . it looked as though old Klauth himself had come calling!"
Or the shorter variant (used to describe butchery): "Regular Klauth work!"
A very controversial wyrm, least to say. Surely he still very much Chaotic Evil. But known be extremely paranoid about any other chromatic dragons, seen every single one of them as an adversary, and slaying great many of them. He is also not in a "friendly" relationship with Tiamat. As he surely not planning to die. Quite opposite. He is know to steal eggs from other red dragons, as those are primary component for old powerful netherese spell. That not only allow him to to grow bigger and stronger (faster than dragons do naturally), but also prolongs his natural lifespan... which known to be shorter for chromatic dragons (Tiamat not known be very patient).
Although his exact age is not known, he is surely over an age that red dragons can live (2,500 more or less).
He also not a fan or Dragon Cult. Neither of old day, nor with their new agendas. And more likely would assist undermining them, and surely not assisting them.
Nowadays he lives far more north from Baldur's Gate. Players at least surely wouldn't have an opportunity traveling near his lair... which is good, would they aware or it or not. he is surely far from been hospitable. Although he is know to be patient towards those he not sees as a threat, and sometimes even help when on a strange whim.
Putting him physically in game would be... tricky, to say the least. For various reasons.
Most obvious. Too many wanna-be-heros would seek to kill him. Bitching if he would "one-shot" them with single breath attack (and realistically that's exactly what going to happen). Where tuning down his stats just so he can be killed - would simply erase whole thing about him been a legendary wyrm.
He is also would be simply an absolutely enormous dragon. There is no longer Colossal size in 5e. But even a "colossal" doesn't depict properly how huge he is. If colossal creatures usually was 5x5 squares (25ft. x 25ft space), Kauth would be more like 10x10 squares. There simply wouldn't be enough space on the screen to show him whole.
https://www.youtube.com/watch?v=STah7_rz3qgMaybe if only like showing only his enormous head, peeking over a cliff, with players standing at that cliff.
Well, and finally, like i said, even though he is well know among baldurians, nowadays he lives very far north from Baldur's Gate... although he does travel a lot.
But even if he wouldn't be in the game - having lore about him in the book, and baldurians using sayings posted above - would be nice.
Even though he still an evil dragon, he is also surely very clever, and very wise. Known to be a master of divination magic, and keeping tabs on most powerful entities in Faerun, as well as any important events. He is also long since learned not be arrogant (something that red dragons usually known to be, to an extreme measures). He is known to be a patient great strategist.
