Best part about the rifts for me is that you DO have a role in the outcome of what happens in the game. When MAJOR rifts open, there is a massive movement of mobs to strategic points on the map (and you see them on the map. If you mouseover the mob icon (crossed swords) on the map, it MAY give you approximation of its troop movement. So if you get organized really fast -- and people are more than happy to do this fast -- you MAY cut them off. If you don't they go for your strategic points, overtake them, and then move on to the cities. From small villages to main cities. I've seen where the entire map is controlled by the Rift's mob. It doesn't last long, but the public quests (these are automatically popped up on the screen as soon as Rifts' mobs start moving--also auto accepted) are all FAILED for everyone logged in. Not that big of a deal, but you DO want a sense of accomplishment and try to do better next time--as do other Rift hunters. PVP is done as Andy said, but just to add. There ARE Defiance Rifts (if you are a Guardian) that open up but they are not controlled by players. You also don't get flagged for PVP if you want to accomplish pushing them back (also, there are private and PUBLIC quests for these as well). On top of this, there are also BattleGrounds. Defiance seems so much better than Guardians in these and I've been to more than a few of them (over ten) and have yet to win one.