While this group isn't in the comics, there is a group called the Scavengers that the show never covered. In the comic, they're just small group driving around in a van. They are one of the first to challenge Alexandria after Rick arrives, but Andrea (who is still alive and a sharp shooter in the comics) takes them down pretty easily. The writing for the show often expands both the number of groups in the story and the number of people within each group. The River Women, Scavengers, Wolves are all a departure from the comics, but the theme of banding together multiple communities to take on the Saviors is generally the same. Will be interesting to see if there is some twist coming for this new group. I would think between Alexandria, the Kingdom, and the Hilltop that they have enough bodies to do the job. They just need to get their hands on some weapons now.