Omen

Omen is apart of the Outcasts, she believes the shiny tag keeps her invincible from attacks since ever since she obtained the collar, she has never been harmed. This is partially due to the collar being incredibly radioactive and making her body regenerate rapidly before the wound could even cause damage.

She is not a typical second in command, but due to being somewhat in charge of Amber and Copper, Callus uses her often to his advantage. Omen has never taken any blood from Callus, stating the tag is all she needs and Callus isn't too bothered by that, noting how his attacks are the only one that can do actual damage to her. 

Copper and Amber are guards to Omen and Omen has little respect for the two, considering only Copper of real conversation. She forced both of them to take Callus' blood purely for curiosity's sake.

Mutation: The collar she carries giving her extreme body regeneration skills. It is said her saliva and claws can cause radiation poisoning (though this isn't that affective, only for younger cats)