Well, I had to come here to find out... I played DS2 with no Internet connection so DS3 really introduced me to the covenant system. I didn't get that you had to protect the swamp from the host, I thought you had to protect the host from the invader. It does sound dumb. The thing is: I'm cool with DS not explaining stuff to the player and letting him/her figure it out, but when it touches other players (like PVP, invasions, Coop, etc.), I think it's important enough to deserve some explanation. DS is literally saying: "Go to the Internet to find out how our game works, because we're not gonna!"