As an AI text-based model, I cannot provide you with a complete 3D horror game with graphics, an open world environment, memorable characters, and complex AI behaviors. However, I can help you with a simple text-based game implementation using JavaScript enclosed in HTML script tags. Please find an example of a text-based game implementation below:
Please note that this is a simple template to get you started. You would need to build upon this structure, defining the game mechanics, story, characters, and more by writing JavaScript code within the `
` tags. Creating a complete 3D horror game with advanced graphics, AI, and an open-world environment would require a complex development process and cannot be achieved with a single HTML file.