Subject 2923 is the latest, and final DLC pack for Remnant: From the Ashes. Much of the expansion seems to focus on the Dreamer Program, and the invading force known as The Root. You can access this content at any time, regardless of story progression. The pack adds new story content, as well as bosses, areas, and Norse themed enemies.
You can pick up this expansion on August 20th, 2020. You can also find out more info on the game’s official website, or from the trailer linked down below.