Inquiry about Prompt Engineering and Handling Toxicity/Hallucination

Hello, I'm seeking guidance on prompt engineering and managing toxicity/hallucination in scenarios where the system prompt is not compatible with the model. Could you provide advice or best practices for prompt engineering in such cases? Additionally, how can we effectively address issues related to toxicity and hallucination without a compatible system prompt? Any insights or examples would be greatly appreciated. Thank you for your assistance.