When The Shield first hit the scene in WWE back at Survivor Series in November of 2012, they assisted CM Punk in defending his WWE championship against Ryback and John Cena. A sit down interview later on would see the trio of Dean Ambrose, Seth Rollins, and Roman Reigns explain their position as such: they are the "hounds of justice" and they simply seek to right every wrong within pro wrestling.
That turned out to be a crock of shit when it was revealed still later that Paul Heyman had paid them off, essentially making them hitmen for hire, or mercenaries if you want to call it that.
What happened next, though, was strange. They just started doing stuff. Things. For no discernible reason, and with absolutely no direction. In an interview with the Daily Mountain Eagle, Ambrose kind of sort of touched on this:
"No one really came up with The Shield. It's an organic thing. We've never said, ‘This is what The Shield is going to be.' We just go out and let things flow. We do a lot of stuff off the cuff. We are unpredictable, and that's what makes us so dangerous."
Okay, but that doesn't really explain their role in WWE. Thankfully, that came next:
"We are basically paid mercenaries. If someone needs a job done, they pay The Shield. Lately, we've been in the middle of this power struggle that's going on. Triple H has paid us to do a job, and that's what we will do. I'm sure we will be called upon in Birmingham. If The Shield is in the building, we are going to make an impact."
The storyline possibilities are endless with such an arrangement, including the inevitable break up of the group, so this is a win for all involved.
Really, it's nice to know for sure what we've got in The Shield.