Avengers: How multiplayer missions work and what the Avengers Initiative means
Multiplayer is a huge part of Marvel's Avengers, so you're probably wondering how to start playing with your friends as soon as possible. Once you learn how the game splits its multiplayer and campaign, it's pretty easy to know what you can do alone and what you can do with friends.
The first thing to note is the distinction between the campaign and the Avengers Initiative. The campaign missions are completely single-player only, even if there are other heroes on your team during the missions. The missions simply don't work the same as they do in the multiplayer elements of the game so they have to be done solo.
If you want to jump straight into multiplayer with friends, all you need to do is select Avengers Initiative from the main menu and you'll get access to all of the heroes and missions straight away with pretty much no limitations. Since the mode takes place after the campaign, when you select Avengers Intiative from the main menu you'll get a spoiler warning before being able to proceed straight to the missions.
If you want to unlock multiplayer through natural progression through the single-player missions, it's going to take a little bit more time. You'll need access to the War Table to unlock any multiplayer side missions, which will take a few hours of story content to get to. Even then, you'll only be able to play as two out of the six heroes due to them being locked off by story progression. The fastest way to unlock multiplayer is simply to select Avengers Initiative from the main menu.
We wouldn't recommend jumping straight into the mulitplayer elements though as not only are you missing out on some great campaign missions, you'll also have some underlevelled characters and a lack of loot and experience. Unless you're really itching to get into the multiplayer as soon as possible it makes sense to get through the 10 hour campaign and unlock all of the heroes and skills you possibly can. Trust us, there's plenty of multiplayer content to get through anyway so there's no rush on getting started!