If I could have only one giant in my game, it would be the stone giant. Why? Because they’re classic yet flexible. A stone giant can fit in just about any style of campaign I can imagine:
If I want classic high fantasy, stone giants are the mysterious boulder-throwing menaces of The Fellowship of the Ring.
If I want a realistic, low-magic campaign à la Anglo-Saxon England or A Song of Ice and Fire’s Westeros, stone giants help determine the line between natural and magical.
If I want a more mythic campaign, stone giants belong in the halls of Jotunheim just as much as fire and frost giants.
And if I want a non-European-style campaign, stone giants feel perfectly natural in campaigns that draw from Aboriginal Australian, Native American, African, and Thai myths and artwork. (It’s no accident that the stone giant illustrations in most Paizo products owe inspiration to Easter Island heads or African masks.)
The point is, stone giants just work—in almost any campaign in any world.
Speaking of which, since stone giants are easy to find in the mountains, I’ve tried to brainstorm some slightly more offbeat places to encounter them…
When Mans Krieger imported stone giants to finish the Cathedral of Luna, people thought him mad. But the stone giants proved outstanding masons and sculptors. Perhaps too amazing: tensions at the build site over wages and certain “accidents” have boiled over into violence. Now the half-finished cathedral serves as an armed camp for the warring factions. Mans needs someone to keep the peace before the cathedral is ruined or more deaths occur.
Most elves speak of themselves as the first race to master magic (perhaps with a grudging nod to dragons). But the marula elves know better. They call stone giants the First Magic People, having learned summoning and elemental magic from stone giant wise men. These days, the stone giants seem to regret their choice, aggressively guarding their mountains with stone call and otherworldly eidolons.
Bok Morock is a stone giant bounty hunter with a metal stump for a leg and a one-eyed dire bear companion. He carries a heavy crossbow made from ballista parts. It is said the only way to escape him is to flee to the Stairstep Archipelago, as he considers the flying islands unnatural. But Bok has heard the whispers about his phobia, and in his pursuit of his quarry he has brought down more than one dirigible with a well-aimed boulder or crossbow bolt.
—Pathfinder Bestiary 151
Russ Taylor has more on stone giants in Giants Revisited, including some feats that really play up their mystical natures. Also, for a really deep dive into Golarion’s mammoth-riding stone giant culture (and some early Golarion worldbulding), Pathfinder #4: “Fortress of the Stone Giants” is a must-read.