Initially, only the prologue will be available. After completing it, you can play five campaigns, one for each faction. And after completing any of the campaigns, the epilogue will be unlocked (this was discussed somewhere) :).

Added 3 minutes later

The Inferno animations are generally good, although in the case of the Maniac, it looks more like he's hysterically laughing than dying.

I'm not very impressed with the video. Not only the Maniac, but also the Broodmother look mediocre :( (although the first one has a not-so-serious death animation). The Juggernaut and Demoness seem okay :).

It was also amusing that the initial logos took up almost half of the video :).