Mythic Constructor is a GPT tailored towards world-building in fantasy contexts. The AI-powered tool allows users to create, develop, and expand their own unique fantasy universes by generating various elements and intricate details required to create a comprehensive and immersive world. The GPT can be used to craft settings, characters, events, economies, customs, and more, all within a fantasy context. Not only is it beneficial for those involved in writing or role-playing, but also for anyone interested in storytelling, game development, or wanting to create their own fictional universe. Prompt examples suggest the GPT can provide descriptions of different locations like haunted forests, as well as creating backstories for characters such as cursed knights, articulating the complexities of a magical city's economy or conceiving local festivals and their customs. The user is thus greeted with the question 'What world can I create for you today?' thereby underlying the GPT's purpose and potential. Users are required to have ChatGPT Plus to use the Mythic Constructor. The tool's versatility and customization ability, combined with the extensive capabilities of ChatGPT, make Mythic Constructor a suitable choice for all fantasy world-building needs.