Firbolgs look like normal humans on a much larger scale. They are about 9 to 11 feet tall and 800 pounds, and wear their hair long with long beards. They are typically incredibly muscled, with pale or reddish-pink-toned skin, and can have any of the normal human shades of hair color, but are most commonly blonde or red. They distrust most other civilized races, and so they avoid them by living in the forests and hills. They do keep on peaceful terms with most sentient forest creatures, including wood and wild elves.

Firbolgs are distantly related to true giants. While large for humanoids, they are passable (if easy to pick out) in humanoid societies. Alter self is a racial spell-like ability for firbolgs, and they may use it to take the form of a large- or medium-sized creature. In these times a firbolg is a natural soldier; its physical strength allows it to dominate a battlefield in a way few others can. Their variety also allows them to be versatile in their vocation, drawing upon their natural giant magic to get things done. Firbolgs have no natural disposition towards light or dark, and may follow any path. However, given that their homes are often set in natural surroundings, their culture has a healthy respect for the sanctity of nature and generally abhors the use of undead and similar necrotic powers.