In the anime Chaos Dragon, the Black Dragon is a significant non-human entity recognized as the guardian deity of the nation of D'Natia. Unlike other dragons that form a pact with a single individual, the Black Dragon distinguishes itself by entering into contracts with numerous humans simultaneously, granting each contractor a portion of its power known as Dragon Factor. Those who successfully forge this contract and receive its power are then eligible to join the ranks of the Black Dragon Knight Order, a special military force within D'Natia. The organization is closely associated with the dragon, and its members are seen as representatives of the nation's strength.

The Black Dragon exists as a powerful and ancient being that presides over its knight order from a position of authority. Its personality, while not extensively detailed, appears to be that of a calculating entity driven by its own interests. This is evident when it becomes aware that the Red Dragon, the guardian of the country Nil Kamui, has fallen into a frenzied and destructive state. Rather than acting out of altruism, the Black Dragon approaches a character named Swarrow with a specific proposal. It offers a deal, turning the crisis surrounding the Red Dragon into an opportunity for negotiation and advantage for itself and D'Natia. This action suggests a pragmatic and political mindset, treating the chaos as a matter for strategic transaction.

The Black Dragon’s primary role in the story is as a patron and a political actor. As the source of power for the Black Dragon Knight Order, its existence underpins a major faction within the series' conflict. The knights who serve it, such as a recruit named Swallow Cratsvalley, are cursed and seek to be free of the dragon's power, adding a layer of complexity to the relationship between the contractor and the divine beast. The dragon's decision to intervene in the affairs of Nil Kamui by making a deal with Swarrow directly influences the plot, setting events in motion that draw in the main characters. Its motivations are tied to the stability and interests of D'Natia, as well as its own mysterious ends. While the Black Dragon interacts with the human world through its knights and its deals, its own personal relationships are defined primarily by these contractual bonds of power and obligation. Information on its internal development or a detailed list of its unique magical abilities beyond the granting of Dragon Factor is not available in the provided sources.