I've never seen these before, can some1 explain how they work and how to make one? ;)

Well the skills should be easy enough, just hit up Fissure and all it's Synergies. But the basic premise is, you run out cast a bunch of Fissures around the entrance to town and run in, the Fissures animation disappears, but still do damage. Fissure does pretty nice damage too. I'm sure to make it totally BM you add something like Grizzly lol.