Firbolg

Firbolg tribes cloister in remote forest strongholds, preferring to spend their days in quiet harmony with the woods. When provoked, firbolgs demonstrate formidable skills with weapons and druidic magic.

Humble Guardians.

Firbolgs love nothing more than a peaceful day spent among the trees of an old forest. They see forests as sacred places, representing the heart of the world and monuments to the durability of life.
In their role as caretakers, firbolgs live off the land while striving to remain in balance with nature. Their methods reflect common sense and remarkable resourcefulness. During a bountiful summer, they store away excess nuts, fruit, and berries. When winter arrives, they scatter everything they can spare to ensure the animals of the wood survive until springtime.
In a firbolg's eyes, there is no greater fault than greed. The firbolgs believe that the world remains healthiest when each creature takes only what it needs. Material goods, especially precious gems and gold, have little appeal to them. What use are such things when winter lingers and food runs short?

Natural Druids

Firbolgs have a talent for druidic magic. Their cultural reverence for nature, combined with their strong and insightful minds, makes learning such magic an instinctive part of their development. Almost every firbolg learns a few spells, typically those used to mask their presence, and many go on to master nature magic.
Firbolgs who become druids serve as stronghold leaders. With every action the tribe takes, the druids weigh not only the group's needs, but the effect each action will have on the forest and the rest of the natural world. Firbolg tribes would rather go hungry than strain the land during a famine.

Hidden Shepherds

As caretakers of the land, firbolgs prefer to remain out of sight and out of mind. They don't try to dominate nature, but rather seek to ensure that it prospers and survives according to its own laws. Firbolgs use their magic to keep their presence in a forest secret. This approach allows them to avoid the politics and struggles of elves, humans, and orcs. Such events concern the firbolgs only when the events affect the forest.
Even in the face of an intrusion, firbolgs prefer a subtle, gentle approach to prevent damage to their territory. They employ their magic to make the forest an unappealing place to explore by temporarily diverting springs, driving away game, stealing critical tools, and altering trails to leave hunting or lumber parties hopelessly lost. The firbolgs' presence is marked by an absence of animals and a strange quiet, as if the forest wishes to avoid attracting attention to itself. The faster travelers decide to move on, the better.
If these tactics fail, the firbolgs take more direct action. Their observations of a settlement determine what happens next. If the outsiders seem peaceful, the firbolgs approach and gently ask them to leave, even offering food and other supplies to aid their departure. If those who insist on remaining respect nature, take only what they need, and live in harmony with the wood, firbolgs explore the possibility of friendship with them, as long as the outsiders vow to safeguard the forest. If the settlers clearly display evil intentions, however, the firbolgs martial their strength and magic for a single overwhelming attack.

Outcast Adventurers

As guardians of the wood, few firbolgs would dream of leaving their homes or attempting to fit into human society. An exiled firbolg, or one whose clan has been destroyed, might not have a choice in the matter. Most adventuring firbolgs fall into this latter category. Outcast firbolgs can never return home. They committed some unforgivable deed, usually something that put their homeland at risk, such as starting a forest fire or killing a rare or beautiful wild creature. These firbolgs are loners who wander the world in hope of finding a new place to call home.
Orphaned firbolgs are those whose clans or home lands have been destroyed. They become crusaders for nature, seeking to avenge their loss and prevent the further destruction of the natural world.
A few rare firbolgs are entrusted by their clan with an important mission that takes them beyond their homes. These firbolgs feel like pilgrims in a strange land, and usually they wish only to complete their quests and return home as quickly as possible.

Volo's Complete Subrace Handbook; Mordenkainen Presents: Monsters of the Multiverse

Firbolg

ability score increase: Choose one of: (a) Choose any +2; choose any other +1 (b) choose three different +1

age: As humanoids related to the fey, firbolg have long lifespans. A firbolg reaches adulthood around 30, and the oldest of them can live for 500 years.

alignment: Firbolg can be of any alignment

Size: Medium

speed: Your base walking speed is 30 feet.

Languages: You can speak, read, and write Common, Elvish, and Giant.

race features:
Firbolg Magic. You can cast detect magic and disguise self with this trait, using Wisdom as your spellcasting ability for them. Once you cast either spell, you can't cast it again with this trait until you finish a short or long rest. When you use this version of disguise self, you can seem up to 3 feet shorter than normal, allowing you to more easily blend in with humans and elves.
Hidden Step. As a bonus action, you can magically turn invisible until the start of your next turn or until you attack, make a damage roll, or force someone to make a saving throw. Once you use this trait, you can't use it again until you finish a short or long rest. Powerful Build. You count as one size larger when determining your carrying capacity and the weight you can push, drag, or lift.
Speech of Beast and Leaf. You have the ability to communicate in a limited manner with beasts and plants. They can understand the meaning of your words, though you have no special ability to understand them in return. You have advantage on all Charisma checks you make to influence them.

Volo's Complete Subrace Handbook

Bloodbear Firbolg

Firbolgs who have an affinity with the spirit of the bloodbear have longer, shaggier hair than other firbolgs, and have somewhat sharper teeth. They are known for using their ability to transform into the shape of a fearsome beast to protect their clans and withstand savage battles. These brutal, and reckless firbolgs are the first in any clan to run into the fray.

ability score increase: Choose one of: (a) Choose any +2; choose any other +1 (b) choose three different +1

age: As humanoids related to the fey, firbolg have long lifespans. A firbolg reaches adulthood around 30, and the oldest of them can live for 500 years.

alignment: Firbolg can be of any alignment

Size: Medium

speed: Your base walking speed is 30 feet.

Languages: You can speak, read, and write Common, Elvish, and Giant.

race features:
Bloodbear Transformation. Once per long rest, when you are reduced below half your maximum hit points, you regain a number of hit points equal to half your level. You also gain the features of a humanoid-bear hybrid for 10 minutes. Your hair thickens into dark fur, your teeth sharpen and your nails shift into powerful claws. You gain two natural weapons for the duration, your bite, which deals 1d8 piercing damage on hit, and your claws, which deal 1d6 piercing damage on hit. Your claws count as finesse weapons. You also gain a climb speed of 30 for the duration.
Scent of Prey. Bloodbear firbolgs can smell blood in the air like a wild beast. You may use your action to learn the direction of any beast or humanoid below half of its maximum HP within 5 miles. You have advantage on Survival checks made to track creatures whose direction you know. You can track a scent for one hour, or until a wind of a moderate speed disperses the trail.
Once you use this trait, you cannot do so again until you finish a short or long rest.
Speech of Beast and Leaf. You have the ability to communicate in a limited manner with beasts and plants. They can understand the meaning of your words, though you have no special ability to understand them in return. You have advantage on all Charisma checks you make to influence them.

Volo's Complete Subrace Handbook

Ghostraven Firbolg

Gliding in from the darkness on spectral wings, firbolg ghostravens call down dark fates through their affinity with the raven spirits of the Shadowfell. While a firbolg ghostraven can fly in the darkness and it does so mostly to avoid dangerous enemies, terrain, and hazards. They are the informants, and wise sages of the clans.

ability score increase: Choose one of: (a) Choose any +2; choose any other +1 (b) choose three different +1

age: As humanoids related to the fey, firbolg have long lifespans. A firbolg reaches adulthood around 30, and the oldest of them can live for 500 years.

alignment: Firbolg can be of any alignment

Size: Medium

speed: Your base walking speed is 30 feet.

Languages: You can speak, read, and write Common, Elvish, and Giant.

race features:
Ghostraven Transformation. Once per long or short rest, while you are in dim light or darkness, as an action you may briefly become ghost-like until the end of your next turn, gaining a flying speed of 30 feet, and the ability to move through any creatures space. While in this form, your movement does not provoke attacks of opportunity. Attacking or casting a spell ends this effect early.
Curse of the Raven. Once per long rest, as an action you summon raven spirits to distract one creature you can see within 30 feet, who must make a Wisdom saving throw. On a failed save, the creature is cursed; weapon attacks against the target can score critical hits on rolls of 19–20, and the target takes an additional 1d6 necrotic damage from a critical hit. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself, and dissapating the spirits on a success. The save DC is equal to 8 + your Wisdom Modifier.
Speech of Beast and Leaf. You have the ability to communicate in a limited manner with beasts and plants. They can understand the meaning of your words, though you have no special ability to understand them in return. You have advantage on all Charisma checks you make to influence them.

Volo's Complete Subrace Handbook

Primalstag Firbolg

Primalstag firbolgs are proud warriors, leaders and hunters who respect strength, endurance, forthrightness, and skill. They take part in, and allow others to join in Wild Hunts, which often include the entire clan and a group of animals trained to defend the warriors of the clan. They are often seen wearing a headdress or helmet decorated with antlers to signify their affinity with the primal stag spirits.

ability score increase: Choose one of: (a) Choose any +2; choose any other +1 (b) choose three different +1

age: As humanoids related to the fey, firbolg have long lifespans. A firbolg reaches adulthood around 30, and the oldest of them can live for 500 years.

alignment: Firbolg can be of any alignment

Size: Medium

speed: Your base walking speed is 30 feet.

Languages: You can speak, read, and write Common, Elvish, and Giant.

race features:
Stag's Leap. You may use your bonus action to make a 10-foot standing long jump. Your movement doesn't provoke attacks of opportunity while jumping in this way.
You can use this feature up to three times, and you regain any expended uses when you finish a long rest.
Primal Reflex. Your senses are sharp and your reflexes quick, allowing you to turn your opponent’s strikes into glancing blows. Whenever you take the dodge action on your turn and you are hit by a weapon attack, you can use your reaction to reduce the damage you take from the Attack by a number equal to 1d6 + your Dexterity modifier + your proficiency bonus.
Once you use this feature you cannot do so again until you finish a short or long rest.
Speech of Beast and Leaf. You have the ability to communicate in a limited manner with beasts and plants. They can understand the meaning of your words, though you have no special ability to understand them in return. You have advantage on all Charisma checks you make to influence them.

Civilization and Culture

Naming Traditions

Firbolg adopt elven names when they must deal with outsiders, although the concept of names strikes them as strange. They know the animals and plants of the forest without formal names, and instead identify the forest's children by their deeds, habits, and other actions.
By the same token, their tribe names merely refer to their homes. When dealing with other races, firbolgs refer to their lands by whatever name the surrounding folk use, as a matter of tact and hospitality, but among their own kind they simply call it "home." Sometimes firbolgs adopt the nicknames or titles outsiders give them under the assumption that those who need names can call them whatever they wish.