Frost giants are kind of the default giant—big, reliably evil, throw rocks, have scary pets, and with one foot in the “real world” of hill giants, stone giants, and Vikings, and one foot in the more mythic world of cloud giants, storm giants, and Thor. You can play them as the Norsemen’s worst attributes and hungers exaggerated, or you can play them simply as doing what they have to do to survive. After all, winters in the North are long, and it’s hard to feed one giant, let alone a tribe with ogres, humans, winter wolves, and white dragons in tow.
And in fantasy RPGs, the North Pole is rarely a sheet of ice. Fantasy Arctics tend to lead to places like the Para-Elemental Plane of Ice, Niflheim, the center of the (hollow) earth, one of the icy Hells, or the Plateau of Leng. Frost giants are bound to harry and hunt humanity—but they may also be the only things that stand between civilization and things far, far worse.
There is a lost kingdom of elves beneath the ice. But warring yetis and morlocks block the tunnels there. The strangely solemn yetis can hold the morlocks at bay long enough for explorers to reach the elves, but will only do so if their packmates are rescued from thralldom. A frost giant jarl holds them in bondage.
A frost giant oracle communes with the spirits of his land. Always they have guided him well, but recently the whispers he hears call for even more blood than usual. His growing madness disturbs his kin—they fear the influence of a wendigo or the winds from Leng—but the only one who might have stood up to him is a rime-blooded sorceress (Ultimate Magic 72) exiled for her mutated bloodline. Humiliated to be asking for help, the giants send winter wolves to find adventurers who might seek her out or aid the giants themselves.
To control his berserker rages, a barbarian must be trained in a certain feat that can only be learned from a frost giant hunting lodge. This is not completely unheard of—notable taiga giants and winter wolves have gained acceptance—but life in a warriors’ hall scaled for 15-foot brutes will not be easy.
—Pathfinder Bestiary 149
3.5 fans who want frost giants and more should check out Frostburn by Wolfgang Baur, James Jacobs, and George Strayton (and which I have decided not to link to until Amazon starts paying state taxes). It’s definitely the best of the environment books, with great PC races, deities, prestige classes, tribal weapons, and monsters, including three frost giant variants.