Let me first say I love the premise. Good, ok here are some things this reminded me of at least once:
A drunken dnd session
Grimdark fantasy
The librarians
A bioware game
Joe Abercrombie
Terry Prachet
Brutal Legend

As you might have guessed the tone is all over the place. I don't know that this is a problem. The funny is funny and the wow that's dark is dark wow. It'll end up being a matter of taste if you like the mix. Make no mistake though, it's never just a little tonal swing. The wacky situation where you never know if an explosion is a laughing or crying mattter is the story's only consistent flavor.