Dungeons & Dragons: Daggerdale

This can be done online or locally. The way co-op works in this game is you load two existing characters (in local; up to 4 online) or create new characters. The game will jump to wherever Player 1 is in the story. You can play the whole game in co-op if you want, but for this trophy, you only need to complete Chapter 4 in co-op. If you've completed the game, you can replay Chapter 4 any time by going through the portal in the Mouth of the Void again. It's easier to do with two actual people, but you can do it alone with two controllers as well. Just remember to revive the second character with if he/she dies, or you will fail the quest and have to start over.