The developer says it's a mix of a "Turn-Based Roguelike Strategy game with resource management and deck-building elements". You died, you've gone to purgatory and you've done a deal with the devil to eventually exact your revenge on whoever killed you when they eventually come along to purgatory too. Until then, you're exploring and combatting a bunch of otherworldly horrors.
No release date yet other than "soonish". I'm sold already though, what an awesome trailer.
You can wishlist / follow Brutal Orchestra on Steam.