Slitheen are big, green monsters made up of living calcium. This makes them vulnerable to acids like vinegar, and if coated in vinegar a Slitheen will explode. They come from the planet of Raxicoricofallopotorious, and have a habit of farting a lot.Except its not really farting, its actually something called gas exchange. Slitheen use compression fields to squeeze themselves down into the skins of other species, and the gas exchange makes sure that they fit but at the cost of them farting all the time.
Slitheen are hunters by nature, but they also try and grab an easy profit when they can. This means that most Slitheen work as mercenaries, and so very few are associated with the League.