Sabotage Studio has launched its free DLC for Sea of Stars called Throes of the Watchmaker, and like most RPGs, there are a few things you need to complete first. While I’ll go into detail below, you basically need to do the main story up to a point where you’ll get your first breadcrumb for the DLC. So, if you don’t see it from the start, don’t worry. Just follow Valere and Zale’s adventure, and you’ll eventually be able to experience this self-contained journey.
How To Start Throes of the Watchmaker
Before anything else, here’s a small disclaimer: in my case, I started the DLC by loading into my finished save file, that is, the one I used when I completed the base game. With that in mind, it seems that you need to complete the game before accessing Throes of the Watchmaker.

In my case, I got the breadcrumb for the DLC as soon as I loaded my save file in the shape of a message inside a bottle. I got the above pop-up saying I got a letter from Hortence.
If you’ve received the message from Hortence, you can travel to the Verspertine by selecting “Yes.” You can use the image below as a reference.

Once you arrive at the Vespertine, watch the cutscenes, and keep following the story until you enter the new Clockwork land.
Does Progress Carry Over to the DLC?
If you thought you could use your equipment, skills, and combos from the base game, that won’t be possible. Sea of Stars: Throes of the Watchmaker is a self-contained DLC that does not affect the base game, meaning that right from the start, you’ll have a new class, gear, and even a new companion. You won’t even be able to bring some of your party members inside this world. So, if the DLC feels a bit challenging, activate a few Relics until you familiarize yourself with the new systems, currencies, enemies, and skills.
However, Throes of the Watchmaker isn’t that long. You’re looking at an eight-hour playthrough, and that’s assuming you rush it. You can easily spend 10 hours if you decide to solve all the puzzles and complete the many mini-games in the DLC. Once that’s done, you can return to your normal game to beat any remaining bosses, find some chests, or get the true ending.