The eight Metallic Dragons were created in a different manner. Metal is magic - everyone knows this. It's why gold has such a hold on people. It's solidified, condensed, trapped magic. The eight metallic dragons were born from eight metals, empowered and ensouled by others, consciously or accidentally or in dreams. They were raised, created, and set loose; dark mirrors of the chromatic dragons, but in every way their equals.
They are powerful, immortal, and immensely proud, but their creation has left them flawed and incomplete creatures. All dragons love flattery, and all dragons hoard things, but no two dragons are alike, just as no two sunsets are alike. All dragons are intensely magical. They are difficult to kill.
Side Note: There are no "good" or "evil" factions in my setting. It's just... people. I need dragons to suit. Some ideas run by dubious outside consultants.
Gold DragonsDisposition: Vain, Patronizing, Sympathetic, Detached
Common Hoards: Religious Texts, City-States, Palaces, Statues, Masks
Breath Weapon: Paranoia
Gold dragons are the most majestic and desirable of all dragons. They love to be adored. They generate cults spontaneously. All other living creatures are treated with charitable indifference; kindness without empathy... or effort, if possible. Mere proximity to a gold dragon heals wounds. A gold dragon will listen to your story with a kind, smiling face and make a token effort to help you. They build vast palaces and indifferently rule city-states in warm climates. They prefer isolation; the better to ensure nothing distracts their subjects. Gold dragons can breathe paranoia, infesting targets with waking nightmares, lunatic fears, and crippling doubt. They also move with liquid grace and the momentum of a landslide.
Silver DragonsDisposition: Meticulous, Strict, Scrupulous, Persistent
Common Hoards: Wealth in Any Form, Total Collections (one of every bird, one of every beetle), Books, Crippled Fraudsters
Breath Weapon: Sleep
Silver dragons are keen-eyed contract writers and organizers. Their lairs are living memory palaces; each thing has a precise and properly marked place. They despise frauds and forgeries; cities have fallen to the wrath of a cheated silver dragon. Instead of a loose pile of treasure, they build compartmentalized, numbered, and monitored vaults. A well-documented ledger sends them into rapturous ecstasy; tales of broken contracts can rouse them to fury. Their breath causes sleep; sometimes for a few moments, sometimes for years. Cruel silver dragons might sign a contract for a task to be completed in ten years, then put the opposite party to sleep until a few hours before the deadline. They'll never deliberately break a contract... but they are more than happy to engineer situations where the other party is forced to default.
Mercury DragonsDisposition: Passive, Considerate, Self-Obsessed
Common Hoards: Mirrors, Glass, Great Scholars
Breath Weapon: Rage
Alchemists might expect mercury dragons to be fickle. Instead, they are utterly fixed in one way - complete imperturbability. A mercury dragon is never wrong and can never be corrected, contradicted, or surprised. They live in a haze of perfect equanimity, with all possible opinions and actions balanced and given equal weighting. Therefore, they are blessedly inactive. They polish caves by their passing, construct smooth on top of mountains, and sleep with one eye open. They are master tacticians, scholars, and counselors, but their advice will always incorporate multiple points of view. Their flesh is liquid; their touch induces madness and slow tumorous death. Their silver-fog breath sends people into a delusional rage.
Copper DragonsDisposition: Magnanimous, Polite, Dishonest, Sadistic
Common Hoards: Wealth, Shattered Buildings, Supplicants, Slaves, Beautiful People
Breath Weapon: Miserliness and Cowardice
Unlike all other dragons, copper dragons give their hoards away freely. They seem to delight in giving gifts. They might rob, pillage, and extort for a century, only to turn around and release their wealth into the world. Their gifts are never random and always cruel. A poor man will be given unimaginable wealth. The dragon will watch as paranoia, new-found friends, or poor choices conspire to destroy the recipient. They also capture or purchase slaves and delight in giving them to unwelcome owners or arbitrarily freeing them. A copper dragon's breath induces self-interest, greed, and cowardice (via fear of losing one's life). This is their main method of acquiring wealth; they corrupt others into hoarding wealth and then rob them.
Antimony DragonsDisposition: Prudish, Inquisitive, Contemptuous
Common Hoards: Skeletonized Undead, Rare Metals, Severed Heads, Surgeons
Breath Weapon: Lust
Antimony dragons are bizarre creatures. They can shift between a dark, liquid, and scaled "female" form and a dense metallic "male" form with ease. In their "female" form, they move with incredible stealth and can use shadows as portals. In their "male" form, their scales absorbs metal weapons, growing stronger and thicker with every blow. They are disgusted and fascinated by living creatures, especially mammals. They might be temporarily placated by abasement and humiliation, but eventually, they'll destroy any creature in close proximity. Toxic dust falls from their scales as they walk; they will resolutely refuse to believe their dust is toxic. Inside the soporific clouds they breath, creatures find their judgement altered and their perceptions warped.
Side Note: The exact effects of the antimony breath weapon's attack should be carefully adjusted to fit your campaign. Maybe it it breathes marriages. Maybe it breathes cartoonish, dancing-in-the-moonlight love and makes everyone waltz. Maybe it makes everyone tear their clothes off and dive for the bushes. Your call.
Iron DragonsDisposition: Peaceful, Lethargic, Dim
Common Hoards: Shiny Objects, Flatterers, Impressive Statues
Breath Weapon: Violent Death
Iron Dragons know there is a war coming. They are conserving their energy. They rest in bogs or ruined cities, coated in layers of rust and slime. Each one is the size of a castle; some are the size of cities. They leak blood and molten metal. Simple statues of impressive scale and scope flatter them; they have no artistic taste, but all dragons love flattery. Once in a century, perhaps, they could be persuaded to breath instant death onto the enemies of their flatterers, but only if they're convinced it's the best way to prevent a larger conflict. Sword wounds appear instantly. Invisible arrowheads plunge into flesh. The iron dragon yawns and retreats, its skills untested. In fact, they aren't very good at fighting, but when you're the size of a castle and you can fly it hardly matters.
Tin DragonsDisposition: Duplicitous, Shy, Humble
Common Hoards: Criminals, Lost Art, Secrets
Breath Weapon: Overweening Pride
Tin dragons have few virtues and powers. They are typically the smallest dragons. Some are barely the size of a horse. They can't see (heavy scales grow over their eyes) and they fly slowly. Their main power is being underestimated; their breath can convince anyone they are an invincible dragonslayer. All the tin dragon needs to do is play dead or lure the would-be attacker into a trap. Tin dragons tend to be highly religious - another anomaly. They hide escaped convicts, rescue people from persecution, and generally try to be helpful. It rarely works; tin dragons are notorious for doing precisely the wrong thing.
Lead DragonsDisposition: Grim, Stoic, Smug
Common Hoards: Wealth, Bets, Messages
Breath Weapon: Frenzy and Death
The seer dragons. Lead dragons are thankfully rare. They have molten hearts and radioactive eyes. They leak poison and ooze corruption. Few living creatures can spend any length of time near one; their very nature is sufficient protection, leaving aside their thick scales and blunt, crushing teeth. Lead dragons are assured of immortality; they will carry messages forward in time, take long bets, sculpt using stone and water, and wait patiently for problems to solve themselves. They know a great deal about the past. Convince them they are in danger and they'll rise like nuclear fury, shedding white lead and spraying toxins in all directions. They can breath a prickling cloud of invisible gas that first invigorates and then poisons.
Occultum DragonsDisposition: Unknown
Common Hoards: Unknown
Breath Weapon: Unknown but probably apocalyptic
There's never been enough occultum in one place to create an occultum dragon, but someone out there is working on an occultum dragon egg. Whatever hatches from it will be massless, frictionless, and pure directed magic, untroubled by physics or morality.