Firbolg are hearty, lusty people, whose pleasures include ale, mead, beer, wrestling, ordering people about, and chess. They like gold and other precious metals and gems, but they prefer not to have to dig for them themselves. The quality of their non-magical ores is not as good as the Dwarves', and this annoys them.
Typical Firbolg dwellings are large, airy, stone work buildings ranging in size anywhere from cottages to castles.
A player character who happens to have been born a Firbolg can find an adventuring occupation in any of these arenas; Cleric, Druid, Fighter, Ranger, Mage, Specialist Invoker or Necromancer, Thief, or Psionic. Also, any two of these except Cleric/Thief and anything/ Specialist.
All Giant-Kin speak the same language, also called Jote, and a Firbolg can choose from Ancient, Mer, or any of the other languages spoken in the Shattered Lands. Other languages are possible, but must be explained to the DM's satisfaction. Jote uses the Ancient alphabet.
Firbolg don't have a great deal of imagination, and for this reason, illusion spells don't work very well on them. This gives a bonus to their saving throws against any illusionary effect. This bonus is +1 for every 3 1/2 points of constitution (see Table 9 in the PH). They even get a saving throw if none is indicated. Similarly, Firbolg have exceptional resistance to toxic substances. All Firbolg characters make saving throws with the same bonus they get against illusion spells.
Because of this imagination problem, however, Firbolg have trouble using illusion-producing magical items. All such items have a 20 percent chance to malfunction when used by a Firbolg. (See the description in the PH on Dwarves for the rule on this problem.)
The Firbolg have infravision to 30 feet in darkness.
Since the Firbolg are so tall and their legs are so long, they have a movement rate of 15.
Because of their size and build Firbolg get to add 1 to their strength. There is a cultural emphasis on thinking and strategy which translates to an additional 1 point of intelligence.