Usually the challenge with good monsters is differentiating them from one another—how this good agathion differs from that good lammasu…or that good angel…or that foo manatee…or whatever.
That’s not a problem with silver dragons. The members of Draco nobilis argentum have always been shapechangers and meddlers. As far back as 1e a silver dragon, Silvara (of course), was one of the tragic figures of the Dragonlance setting. And when Dragon Magazine #146 introduced the new, beefed-up 2e dragons, it was via a group of adventurers trading dragon-slaying tips with a Sterling (again with the obvious names) and Hypatia, who were then revealed to be silver dragons.
Pathfinder’s silver dragons have taken on a new role courtesy of Mike McArtor’s work in Pathfinder and Dragons Revisited: dragonkind’s paladins. In DR, silver dragons are righteous and often religious warriors with a yearning for restrictions, rituals, and mentors (oddly, from other species—typically gold dragons or lawful good outsiders). Their craving for missions and mentors means they have lots of excuses to mix it up with PCs, either as allies, rivals, or even foes.
Why foes? Because silver dragons tarnish easily. The heavy weight of responsibilities placed on them and their constant struggle against evil sullies more than a few of their souls. And a silver dragon that falls from grace falls far, often “degenerating into strange creatures that resemble draconic crossbreeds,” according to DR. In other words, if you want your PCs to fight a metallic dragon, silvers are the way to go, and don’t hold back on swapping out abilities or adding templates. Just as the best blackguards and death knights are former paladins, the best dragon to fight your PCs might just be a silver with its scales and spirit corroded unto dull, lifeless rot…
Craving the spiritual security of strong restrictions and stronger penances, a silver dragon left his lammasu mentor for a more stringent guide. Now he serves (and bears the marks of) a scourge-wielding cavalier who may be a Knight of the Thorn’s Song…or who may be an erinyes carefully leading the silver dragon down a lawful road that has no mercy or light at its destination.
The Wight-King of Lemoria stirs, and a council of silver dragons is eager to lead an army to war. In their zeal, they aspire to hold open the Bridge of Seven Spires for their soldiers to cross…and that means thwarting a group of equally good-hearted (if far less noble) adventurers recently charged with demolishing the bridge to hem in the Wight-King’s undead hordes.
When the noble and much-noted Argidox tarnished, it is said that even the chattiest brasses fell silent in horror. Now the ancient silver dragon has scales the color of rain-washed lead, and instead of control weather he wields plague storms and scouring winds (see Ultimate Magic) instead.
—Pathfinder Bestiary 110-111
Back from the beach! We now resume our regularly scheduled monsters…