Doom Kitty is the secondary main character and possibly the other deuteragonist of the Ruby Gloom series, She is Ruby's pet black cat. She wears a red ribbon around her neck along with a little gold key with a heart-shaped hole. She has a complete free run of the mansion and is therefore usually the only one with total knowledge of what is going on in any given area of the house. This keeps her one step ahead of Ruby and the others most of the time, because whenever something strange happens in the mansion, Doom will usually have all the facts already while everyone else is still trying to figure things out. Unfortunately, since Doom can't talk, her only hope of communicating with the others is through charades. Ruby usually has a pretty easy time understanding her, but it doesn't always work. This shows that Doom hates it when she is trying to communicate, and her friends think she is playing charades.