"It's your mark on the world," Duncan said. "The core vision of it is players going on adventures together."
That idea morphed into Sea of Thieves, a cartoonish, tongue-in-cheek pirate game, in which players travel oceans together in boats, exploring underwater ruins and searching around islands dotted throughout the world. "It can be a genuinely magical experience," he said. "It can give you an experience that's unlike any other."
Sea of Thieves is part of a new genre of video games designed to entice people into living worlds meant to be played for hours on end. Inside the industry, they're called "games as a service" or "live service games." But to everyone else, they're a chance to play a favorite game to their heart's content.
This idea is far from new. Adventure games like 1999's EverQuest and 2004's World of Warcraft became cultural phenomena, attracting millions of people who not only played the games but also bought related books and merchandise for decades. Millions even went to see a feature-length film, appropriately called Warcraft, in 2016.
But in the last couple years, more companies have created their own takes on the genre. Many were on display at thelast week.
Bethesda Softworks has The Elder Scrolls Online fantasy epic and Fallout 76 post-apocalyptic survival game. Electronic Arts launched its Anthem adventure game earlier this year. Bungie, maker of the industry-defining Halo series of games, now offers a space battle epic called Destiny. And Epic's Fortnite battle royale last-man-standing game has itself become one of the most popular in the industry.
"There's clearly a group of people -- and I would go so far as to say it is a large group of people -- who are very much into investing in something they can invest in and get what they want out of it," said Pete Hines, head of marketing at Bethesda. "They get back fun, entertainment, social connections, a feeling of progression and whatever else they're looking for."
It's not all happiness and roses, though. Companies say that as they've entered the genre over the past few years, they've learned these games are harder to create and maintain than they'd expected. The pressure to keep fans happy with new stories and experiences, while also finding ways to pay for the teams and technology that powers them, has led to trouble.
Some games, like Anthem and Fallout 76, have drawn criticism for launching with too many bugs and not enough enticing things to do. Gamers aslso criticized Take-Two Interactive Software's Rockstar Games division over how Red Dead Online initially pushed people to spend real money to more quickly acquire guns and horses needed to play the game. (Rockstar has since changed the way the game works.)
"The industry is getting worse in a lot of ways, they're getting more predatory and more exploitative," said Steven Williams, a longtime gaming commentator whose YouTube channel, Boogie2988, has more than 4.5 million subscribers.
He and many other commentators say companies aren't thinking enough of gamers or employees when creating these titles. They're asking too much money for extra experiences, storylines and items, while giving back too little, he said. Stories of employees working seemingly nonstop to satisfy gamers' expectations has also worried him.
And many of these gamers say new business models go over the line. One in particular, known as microtransactions, asks players to pony up real money on top of the original cost of the game to pay for extra designs for characters and weapons.
"We've got $60 games with $120 special editions, and microtransactions too," Williams said. "It's the nightmare scenario we were all warning about and now we're there."
While Williams said some gamers' criticisms can go over the line, there is some merit to their concerns.
Game makers counter they're learning as they go and frequently end up apologizing and attempting to make good with their community when they screw up. But they also say they're answering players' requests to create game worlds they can explore for longer periods of time with their friends.
"We're trying to figure out what will engage and captivate," said Strauss Zelnick, head of Take-Two Interactive Software, which offers online additions to 2013's Grand Theft Auto V and last year's Red Dead Redemption 2 cowboy game. (Zelnick is also interim chairman of CBS, which owns CNET.)
Zelnick said his teams aim to offer "more value than we charge," he said, even if it doesn't always come across that way.
"You don't want players to say, 'I really, really love the game, but...'" he said. "You want them come back and say, 'I really, really love the game and sure, I had to pay for it, but it's appropriate to pay for great experiences.'"
While it may seem to some gamers that these games are taking over the industry, developers are still producing self-contained titles too. Some of the upcoming ones include EA's The Last of Us Part 2., Nintendo's forthcoming sequel for and Sony's survival thriller
Meanwhile, developers are figuring out how best to make this new breed of live-service games too. And as more of them are made, another problem is that there are so many on the market, it's hard to decide which one to play.
"This space is so new," said Matt Firor, game director for The Elder Scrolls Online. So his team has designed the game to be more welcoming to people who only play once in a while. For example, people who haven't advanced far in the story can still play alongside dedicated players who've done nearly everything they can.
"Most of my friends have a main game they play," said Sam Kirkendoll, 29, who works in fundraising for a university in the Dallas-Fort Worth area. He's been playing World of Warcraft since 2007, but he said other friends dabble, leave and then come back.
Firor, of The Elder Scrolls, learned that what brings back those dabblers are big updates with lots of new stuff to do. So his team has started hyping big launches of new stories much the same way TV producers market new seasons for their shows.
"You just need to keep innovating and bring new type of experiences," said Kati Levoranta, CEO of Rovio, maker of the hit Angry Birds mobile game. The company's tweaks and new things to do haven't just enticed existing players back, she said, they've brought new ones in too. As a result, the number of people who have played Angry Birds 2 every day has continued to increase, despite it being four years old.
"We know the world where we live today is quite fast-paced, and there are new things coming along all the time," she said. "So you need to keep yourself fresh and relevant."
Keeping them happy
Game makers said one key to making it all work is giving players a way to offer feedback and then responding with tweaks as they go.
"You learn over time, because you always have the community giving you feedback," said Yves Guillemot, CEO of Ubisoft, which makes The Division 2 post-apocalyptic paramilitary thriller and Tom Clancy's Rainbow Six Siege strategy game. "We can learn what they want and adapt content to what they need."
Rare's Duncan released the game's biggest changes in April, a year after its initial launch. The update included storylines called Tall Tales, which were developed with the help of dedicated players who tested the changes and gave feedback. The company also put out regular videos to the community to keep them apprised of how development was going, up to its launch.
"Sea of Thieves today wouldn't be the game it is without the journey we've been on in the last year," he said.