From the post:
Of the four types of Xenos the scientists have been able to identify, the Workers are the weakest. However, that’s not saying much. They can still easily rip a human in two. Workers tend to attack in packs, and if the Survivors are not careful, they will quickly be overrun.
The Workers will start their assault on the PK-L7 mining base when Zombicide: Invader comes to Kickstarter on April 10 at 3 PM EST.