I think it can't be generated yet.
Development of AI:
Text generation →
Art generation →
Photo-realistic image generation →
Video generation →
(we are here)
Multimodal generation (voice + image + memory) →
Task-solving AI agents →
AI-generated friends, lovers, teachers →
AI-generated movies, games, science →
AI has became concious →
AI-powered robots among us →
AI dominates the Earth →
AI dominates the space →
Finally AI can create sprites in Tibia style.
The best method I saw so far is to generate image of your monsters in Chat GPT, change this image to 3D model using other AI, load model in Blender and make perspective 45 render. Then you can try to make variants or bone animation in Aesprite using pixellab.