A mask concept trained by the artist Otochichi. I didn't see a Illustrious lora like this yet, so I went ahead and made one. Pretty simple lora. Furry characters can work, but it'll can generate with mixed results due to the type of animal your trying to do generating the nose accidentally or fusing the mask with their mouth. Works perfect on human characters as intended. You can specify the mask color, but changes are it'll mostly be black. You can also combine this with a vacuum lora and it'll work great.

Positive Prompts: FelMSK, mask, masked face

If you want the their head you can do "head strap or hook strap". If you want the mouth to stand out more, then put "silver mouth"