Assassin’s Creed Odyssey takes PS4 players all the way back to Ancient Greece during the 5th century BCE, when Athens and Sparta were locked in a war that would shape the course of Western civilization for millennia to come. Your role in the Peloponnesian War, however, isn’t to work in the dark to serve the light as an Assassin. Set hundreds of years before the events of Assassin’s Creed Origins, Odyssey instead casts you as a mercenary, free to forge your own path and build your own alliances. And that means the introduction of something new to Assassin’s Creed: the freedom to make story-altering choices.

The first such choice is who you’re going to be, because Assassin’s Creed Odyssey lets you pick one of two Spartan mercenaries as your hero: Alexios or Kassandra. The one you choose at the outset will be the protagonist throughout the course of the game, but don’t worry – Alexios and Kassandra are evenly matched. Your chosen mercenary will follow the same storyline, captain the same warship, and wield the same formidable abilities gained from the mysterious Spear of Leonidas. Any differences between the two are largely determined by your actions and decisions during the story.

“The main story is going to have branching,” says Game Director Scott Phillips. “It’s going to come back together so that you have similar choke points where certain events will occur, historical events that we’re not going to change. But there are many, many other choices where [different players’] games will diverge dramatically. And then if you look outside of the main path, if you look at what you’ve done in the world, what choices you’ve chosen to make for other quests in the world, you’re going to see a dramatic shift in how the world perceives you, and what’s available to you because of what you’ve done.”

In a series structured around genetic memories of historical events, this degree of choice is made possible by what the developers say is “old and imprecise” DNA, which leaves it to you to fill in the gaps in the historical simulation. Your options range from dialogue choices and romantic possibilities to much larger decisions: which missions to take on as you work toward a larger goal, for example, or even whether to ally yourself with Sparta or Athens in certain struggles. The demo playable at E3 this week offers a taste of what’s ahead; set on the islands of Delos and Mykonos, it tasks you with a central goal: kill a brutal ruler named Podarkes, who’s backed by Athens and hides behind formidable security.

To bring him down, you’ll need to lower his Nation Power by killing soldiers, destroying supplies, and stealing treasure – and the quickest way to do that is to work with a ragtag group of rebels led by Kyra, a young revolutionary, and Thaletas, a Spartan commander with only a handful of soldiers. Kyra prefers stealthy sabotage, while Thaletas likes to go in guns blazing… er, javelins flying. Whether you want to sneak into enemy camps or take to the seas and sink a few ships, you can pursue either strategy or both, and each tactical choice will bring you closer to Podarkes (and closer to Kyra and/or Thaletas, if you’re interested in pursuing a romance with either). And when the job is finally done, you’ll get to see the effects your decisions have had on Mykonos and the people who’ll still be there after you’ve left.

All of these events are just a tiny slice of Assassin’s Creed Odyssey’s much larger adventure. To find out what else lies in store when it launches for PS4 on October 5, stay tuned for more updates during E3.