In an interview with IGN, Bungie writer Luke Smith says that raids will be six-player missions that open up at level 20; they lack waypoints to tell you where to go and what to do. According to IGN, they're also friends-only, no matchmaking. Smith also promises monsters and situations that "demand of you things you've never even really been asked to do in a shooter before." Think Halo 3: ODST's Firefight mode meets World of Warcraft's Ulduar (or Naxxramas, or Icecrown Citadel, or <insert your favorite raid here>).
"I think the E3 experience video had the narrator talking about the hardest thing we've ever built and we showed a jumping puzzle," Smith told IGN. "Like, the hardest thing we've ever built is a jumping puzzle? The jumping puzzle is just one part but it's this interesting representation of the philosophy behind a bunch of the raiding which is taking something simple, something that you've done, you understand, and then asking six of you to do it together. In a nutshell, that's some of the philosophy that was driving raid design as we were building the first raid in Destiny."
You heard the man: call up your friends and tell them you've got jumping puzzles to solve and monsters to shoot on September 9. After all, you don't want to face your Destiny alone.