Topic: Gaming and Gender names

Dear folks who are respectful of preferred genders...

I play a breeding game, Ark. Some pets have no gender, and can breed with any member of it's/their species. I like to put 'Ms' for my ladies, and 'Mr' for my dudes in other species.

Do I name the non-gender as Mx, or something else? I been naming them Mx, but dont want to be offensive.
Opinions appreciated.