Cosmos is a member of the Garou Knights, the most powerful executioners of Fiore. She has no problem executing people labeled as a criminal by the Kingdom of Fiore. She also has a habit of using the word "beautiful" frequently.
Cosmos uses Plant Magic. This Magic allows her to summon plants to be utilized during battle. Each plant can produce different effects and attacks and can appear anywhere she wishes them to.
(Source: Fairy Tail Wikia)