Killzone: Shadow Fall DLC expansion Intercept has been announced for release in June, and it brings an online four-player co-op mode to the table.
The aim of the mode is to intercept military transmissions from the enemy and relay them to your own side. Obviously you'll be harried while you do so, and that's where the new character combat roles come into play.
They are Assault, Marksman, Medic and Tactician. It's fairly obvious what they do, apart from the Tactician, which deploys sentry turrets and defends locations. The opposing Helghast will have their own combat roles, and they can call on champions - based on key Killzone single-player characters - to beat you up.
The better you work together, the more points you'll get, and you'll be able to unlock artillery strikes and jetpacks.
Intercept will be free for Season Pass holders, because obviously there'd be a riot if it wasn't, and there's a standalone version of the mode planned, too. That's a version you can play without owning the full Killzone: Shadow Fall game, and it's coming later this year.