Ten people died during The Walking Dead's fair in the season 9 episode, "The Calm Before", and it will eventually become the impetus for the Whisperer War. After Andrew Lincoln exited The Walking Dead as Rick Grimes, the Saviors' story and role as the series' villains had come to an end. And in order to really show that The Walking Dead had moved on, a six-year time jump occurred that set every character and every community on a new path.
Part of that new path meant coming in contact with another adversarial group - the Whisperers, who are led by a person named Alpha. After the Whisperers' first altercation with The Walking Dead's core characters in the season 9 midseason finale, a string of events - namely Lydia's capture, release, and escape - culminated in the Whisperers secretly attacking the Kingdom during the first-ever inter-community fair. And that, unfortunately, led to several major deaths in The Walking Dead season 9 episode, "The Calm Before".
In "The Calm Before", 10 characters were killed off, including multiple big names that have been a part of The Walking Dead for many years. The 10 characters killed by Alpha and the Whisperers are: Ozzy (Highwaymen), Alek (Highwaymen) D.J. (Alexandria), Frankie (Alexandria), Tammy Rose (Hilltop), Adeline (Hilltop), Rodney (Hilltop), Tara (Hilltop), Enid (Hilltop), and Henry (Kingdom). Yes... Henry. For Carol, this moment is a repeat of the season 2 midseason finale in which she discovered her daughter, Sophia, was killed and had already turned into a walker.
While more than 10 people died throughout the episode (namely the people from Hilltop who were going to the fair), Alpha and her Whisperers killed 10 people and placed their reanimated heads on pikes in order to mark their territory and send a message to all the communities who would oppose them. It's worth mentioning that this number is down two people compared to the comics, but that doesn't mean it's any less effective. Plus, in order to retain the shock-factor, instead of killing off Ezekiel (which was teased when Alpha/Debra found him at the fair), it turns out killing off Henry was a much more gut-wrenching choice.
In reality, this is one of the most brutal and heartbreaking episodes of The Walking Dead to date, and the fact that it's the penultimate episode in season 9 means that the producers behind-the-scenes have learned their lesson from the season 6 finale, in which they held off on revealing who was killed until the season 7 premiere. Things have changed on The Walking Dead, and it seems a war with the Whisperers is only getting started. Alpha's pikes may only be the beginning.