Draconic Rivarly: The dragon is the rat creature's natural enemy. Were it not for the protection of the dragons, the rat creatures would have gladly massacred the people of the Valley many years ago. Nothing makes a rat creature’s blood boil faster than the reminder of dragons, but nothing makes them scurry in fear faster than the presence of one.

Warband: Despite their animalistic nature, rat creatures are surprisingly organized when in groups. You will rarely see any less than two rat creatures at a time. They refer to each other as comrades, believe in a hierarchy of power, and bow to a supreme ruler. They travel together, hunt together, and when the opportunity arises, they go to war together. They even have a secret language known as Nessen, specifically meant for wartime messages and raids, and believe in treaties and negotiations.

Dim Witted: When encountering rat creatures for the first time, it is a common mistake to underestimate them due to their lack of intellectual prowess. Some rat creatures can be clumsy and easily distracted. They have tendencies towards cowardice, greed, and anger. It would be foolish to take this at face value, for they could fall upon you without warning.

Pack Tactics. The rat creature has advantage on an attack roll against a creature if at least one of the rat creature’s allies is within 5 feet of the creature and and the ally isn't incapacitated.

True Comrades. The rat creature gains advantage on Wisdom and Charisma saving throws if it can see another rat creature within 30 feet of it. If no other rat creatures are within sight, the rat creature has disadvantage on all Wisdom and Charisma saving throws.

Lurking in the shadows of the forests, mountains, and valleys lie in wait the starving rat creatures. Also called Hairy Men, these carnivorous, shaggy haired, greedy, and cowardly ape-rat chimeras live in a constant state of hunger and viciousness. Rodents, birds, and other wildlife may make tasty snacks, but a rat creature is always on the hunt for something a bit bigger. All adventurers, especially the short ones, should beware when traveling through the thick brush at the dead of night, less they be ambushed by a blur of claw and fang.

Faithful Friend. When a creature within 5 feet of the rat creature cub makes an attack against a target other than it, the cub can use its reaction to make a melee weapon attack against the attacker.

Isn't this a rare sight. Instead of a ferocious beast blindly attacking with tooth and claw, you have stumbled upon a small bundle of hair. It's ears not yet cropped and tail not yet removed, as is customary in rat creature culture. It is also not yet capable of speech, but seems to understand well enough. Rat creatures are not born vicious, but instead learn such behavior as a way of survival. Because of this, their cubs are not hostile at the get go, instead seeking the same companionship all rat creatures enjoy. If the cub is separated from its pack, one could even attempt to befriend it.

I'll Get You There. While being mounted by a non-hostile creature, the rat creature's speed increases by 5 feet and has advantage on Dexterity checks and Dexterity saving throws.

Faithful Friend. When a creature within 5 feet of the tamed rat creature makes an attack against a target other than it, the tamed rat creature can use its reaction to make a melee weapon attack against the attacker.

Now this is the rarest site of all. Some rat creature cubs never fall into the savagery of their people, and instead create bonds with other races. When grown, they are similar to any other in build and ability, but they find it far easier to control their carnivorous impulses, and prefer the company of non-rat creatures. They are then considered a traitor among its people for all time, unwelcome. Thus, a tamed rat creature loses the Hunger and True Comrades features, but gains the following:

Kingdok

There is only one rat creature that all the others fear and respect. One they follow without question, lest they be made an example of. Their lord, leader, and champion. Kingdok is a formidable foe to any foolish flat-lander who dares challenge him. Unlike the rest of his race, Kingdok is a fearsome juggernaut. A hulking mass of muscle and fur with the temperament of a dictator. With his massive, powerful jaw he crushes and eviscerates his enemies and prey. But do not mistake him for just a mindless brute. He is the king of his people, wise and adept at wartime strategy. They proudly rally around him, and while most rat creatures are naked without their comrades Kingdok requires no assistance. He charges alone if he has to, and does not shy away from doing dirty work himself.

Cruel Iron Claw: Kingdok is not a kind monarch. His people only understand strength and brutality, so he rules them with exactly that. Fear is what keeps them in line more than loyalty. Should any of his underlings ever disobey him, they will not live long enough to boast. This makes his position of power absolute. All rat creatures know that to challenge the will of their sire would be folly. If branded traitors, their only hope would be to desert.

Undying And Bitter: It should be a surprise to no one that this huge beast is a difficult thing to take down. But Kingdok surpasses even the expectations given by his imposing build. Even through mutilating injuries he pushes on. Even when suffering blows that would kill others of his size, he pushes on. And worst of all, he does not forget. If you are ever able to somehow injure Kingdok, it would be in your best interest to finish the job.

Cowardly Puppet: The king is not without his weaknesses however. Huge though he might be, he is still a rat creature. Dragons infuriate and terrify him much like any other. He is also arrogant, underestimating any smaller race he considers as weak. Some even hold rumors that he is not the one truly controlling the rat creatures. They say that he is enslaved to a darker force, one that pulls his strings and ensures the rat creatures will bring about the fall of the kingdoms of man, to make way for the era of locusts.