Full of optimism and very constructive, Helck is a fantastic fantasy manga.
The cast plays off of each other very well, and the main duo of Vamirio, one of the 4 Heavenly Kings of Hell, and Helck, a hero of humanity, is probably one of the best in the medium as a whole.
Each one supports the other, and especially seeing Vamirio bring Helck back from the pits of despair over and over, hits just as powerfully each time.
And his genuine support and respect towards her balances things off greatly.
The humor is worked into the manga well, with some genuinely hilarious jokes, and the inclusion of many joke chapters in the volume releases that you can read as you feel the need, helps to balance off any down feelings in the more serious latter half of the manga while not destroying the atmosphere of the actual story.
Gags from early on in the manga become worked in as serious plot points later on, which depending on your demands for the story to take itself totally seriously in that manner, can be bothersome. However, I found it to be very smart writing myself and something that only looked obvious in hindsight.
The action is well done and the choreography, while never particularly complex, is clean and comprehensible. Fights are rather simple and straight-forward.
The cast is incredibly competent across the board, both villain and hero. Making the action enjoyable for showing off the best of both sides. The struggle is rarely in terms of the cast not being able to beat the enemies as they are all very strong and the story makes no attempt to change that, but in terms of them being able to deal with the plans of the villains outside of direct fighting or the emotional toll of having to fight against what the story poses.
While there are references to Levels for characters, they don't mean much at all other than be vague representations of the cast's strength. There is no game-ification of the world.
Much of the fantasy and the races are novel and the manga doesn't parrot Tolkien or Wizardry as many others do.
The twisting of certain 'stock races' is very well done in the places where it happens and works to certainly set the manga apart.
The manga is one that doesn't become depressing or have a ton of bad ends. It is an optimistic work at its core and that is largely the point of it. The manga is built around seeing the light at the end of the tunnel and fighting through all of the darkness with hope and love for those around you. Even in its darkest moments, and Helck does become a very depressing manga at times, the work swings around to bring things back to a happier place.