Destiny's 6-player raids won't support matchmaking, meaning they'll only be playable with friends.
Bungie writer Luke Smith told IGN: "Raids are a really big bet for us. It's a bit of a risk because the activity requires you to have a group of five other friends to play with."
Smith said that raids will likely take a few hours and will often take multiple attempts to complete.
"We don't adhere to any of the standard rules for the rest of the game. Like, raids don't have waypoints, they don't tell you where to go, they don't tell you what to do.
"Obviously we're going to have big cool bosses," Smith added. "I think that we've given people a taste in Strikes of what the bosses are and what they can do. The raid bosses are different: they're still big monsters, much like what you're going to see, they're still scary, but they have a bunch of abilities that are unlike anything you've really experienced in a shooter before.
"I don't say that to be a douchebag and I don't say it because it's a cool bullet point, I say it because when we were building this thing there was nothing that any of us could go home to play to try and learn from. I mean we were - as we were going - building and learning and failing along the way to find cool mechanics and occasionally we'd succeed."
The Destiny release date is September 9 on PS4, PS3, Xbox One and Xbox 360.
July's Destiny beta attracted 4,638,937 unique players, publisher Activision said on Wednesday.