As an example of awesome, look at this pic:-
Every one of those purple swirly things is a Rift. These are public events that everyone joins in on and completes. They spawn the crossed swords, too.
Every one of the square things is a Foothold. This is where the Rift creatures have placed down (or conquered) footholds on wards etc. I'm not sure if they spawn the crossed swords, but I'm fairly certain they do.
Every one of the crossed swords is between 2 and 6 hard (sometimes elite, sometimes just difficult) mobs that run towards the nearest wardstone to capture it. These create footholds which spawn more of these.
This was the beginning of the "big" (there are smaller ones that come along more regularly and are easier to defeat) death invasion. By about halfway through the invasion, my map was literally covered in a sea of purple swords. People were holding off the sheer masses of undead converging on one of the objectives (the other was taken out fairly early on due to a lack of defence) whilst others did Rifts and killed super elites that were running around in order to power some giant cannon thing.
After a LONG time, we completed it. It was hard, it was fun and it actually kinda builds a sense of community and pride in your fellow players.
It was absolutely amazing, hectic and crazy. It's an example of what makes Rift the best themepark MMO to date, too.
If we'd've lost, I think we'd've had about thirty minutes of undead running rampant through the zone, slaughtering quest givers and basically fucking up playing for a bit. :p
You guys should join me.
EDIT: By the by, Rift does amazing dynamic landscape change. When the event started the zone went seriously dark, I could barely see beyond about 100 meters around me. I could still see the rifts tearing open in the sky in the distance, though. It was AMAZING. I wish I could've got more pictures.