Beorn can only specialize in Nature classes: Ranger, Druid, Fighter or Barbarian.  Under special circumstances the DM may allow for a Rogue, Mage or Cleric class but these are at a decided disadvantage.  

Barbarians:  Misunderstood as the Beorn are, many often think of them as wild barbarians.  However, these gentle giants often follow less aggressive pursuits.  Still some do become Barbarians, Beorn a fearcily protective their forest and friends.   

Fighters: Beorn are the guardians of the forest.  Often times these giants take up posts as soldiers watching over their land.  Beorn have fondness for those that dedicate their lives to the protection of others.

Rangers: Hunters, the Beorn make their living in the woods and often become professionals as Rangers.  It is through the Rangers that Beorn stay connected to the world.  

Druids: More than a 3rd of all Beorn are Druids.  A magical connection to the life force of the forest and deep respect for all living creatures sits at the bottom of these souls.  

DM PERMISSION ONLY:

Rogues: Beorn are not concerned with financial gain and will seldom become thieves or treasure hunters.  They do seek out magic and power to protect their realms but not for their own gain.  Generally speaking, a Beorn will look at the rogue with pity and a but of humor.  Like a cat chasing a ball of string.  It's pointless but funny.

Mages and Sorcerers:  Beorn almost never become these academic elites.  They do not feel comfortable in the urban schools and the free spirits are a challenge to any master that would teach them the ways of magic.  The Beorn, however, hold these scholars in high esteem and see there path as worthy.  While wisdom tells them that many of these magi cannot be trusted with the the power they wield, they non-the-less respect their goals.

Clerics: Beorn never become true clerics, some have been called shaman but they do not follow the gods of men.  They are creatures of the forest, like the Fae.  A Beorn, can work with a cleric but is always suspicious of his motives.  

The lifespan of the Beorn is between 150 and 400 years. To achieve their great age a Beorn must hibernate at least every other winter until they are 10th level. At 10th level and beyond they need only hibernate once every 5 years. Hibernation is usually around 3 months of uninterupted sleep.

Beorn are wanderers and they have made homes in virtually every corner of the globe.  Typically a Beorn reflects the environment he|she is from so Beorn born in temperate zones are typically Black or Brown, while those born in the colder polar regions are White.  

Languages: Beorn can speak, read and write: Common and Sylvan

Keen Smell. The bear has advantage on Wisdom (Perception) checks that rely on smell.

At 3rd level the Beorn grows.  Physical Size Increase - Add 1 foot to Character Height and 40 Pounds to Weight.  All existing armor and clothes will need to be altered or replaced.

Level 5

Beornings can use its action to polymorph into a medium bear, or back into its true form, which is humanoid. Its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies. When you shift, you gain temporary hit points equal to your level + your Constitution modifier (minimum of 1 temporary hit point). In this form you can understand common but not speak it (unless you have class abilities that allow it)

While in this form, a Beorning use class abilities except spellcasting and ranged weapon attacks. When a class ability specifies the use of a weapon, a Beorning in Bear form can use its bite attack instead. Note: this does not apply to Pact of the Blade and Hexblade Warlocks. Consult your DM iff uncertain.

Once you use this ability, you can’t do so again until you finish a short or long rest.

At 8th level the Beorn grows again. Greater Physical Size Increase - Add 1 foot to Character Height and 40 Pounds to Weight

Lvl 8: Character is now a Large Size and moving more toward her wild self

At Level 8

Beornings can use its action to polymorph into a large bear, or back into its true form, which is humanoid. Its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies. When you shift, you gain temporary hit points equal to your level + your Constitution modifier (minimum of 1 temporary hit point). In this form you can understand common but not speak it (unless you have class abilities that allow it)

While in this form, a Beorning use class abilities except spellcasting and ranged weapon attacks. When a class ability specifies the use of a weapon, a Beorning in Bear form can use its bite attack instead. Note: this does not apply to Pact of the Blade and Hexblade Warlocks. Consult your DM iff uncertain.

In bear form, you gain advantage on athletics to grapple while in that form.

Once you use this ability, you can’t do so again until you finish a short or long rest.

At Level 16

Beornings can use its action to shapechange into a werebear, or back into its true form, which is humanoid. Its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies. When you shift, you gain temporary hit points equal to your level + your Constitution modifier (minimum of 1 temporary hit point). In this form you can understand common but not speak it (unless you have class abilities that allow it)

While in this form, a Beorning use all his class abilities. 

In werebear form, you gain a bite attack that deal 3d6 + Strength damage, and advantage on athletics to grapple while in that form.

Once you use this ability, you can’t do so again until for a full month.

At 16th level the Beorn grows to full size.  Supreme Physical Size Increase - Add 1 foot to Character Height and 40 Pounds to Weight  Most Beorn at this level stand between 9 and 11 feet tall.

Now accustomed to their large size their dexterity increases.  However, all armor and clothes will need to be altered to account for their larger size.