NOTE: To the downvoters, this is not a religious commentary in any way, shape, or form.
Satania is an utterly unique, 124-page graphic novel by writer Fabien Vehlmann and the artist team of Kerascoët. For my money it's a minor masterpiece, part of a slew of great works these folks did independently and sometimes together.
In terms of plot, the book tracks a hastily-organised spelunking expedition which fails to account for an impending flood. A wiser, experienced explorer, Father Monsore, attempts an emergency rescue, but it's too late, and the spelunkers are swept by the flood deeper in to the caverns until they're thoroughly lost. Then they begin to make unbelievable discoveries one after another, encountering ancient cave art, then a small civilisation of humans, and finally an undiscovered world of furry humanoids and bizarre creatures living above an enormous, bubbling sea of... acid?
This is both a fun but intense read, one that creates a relentless tension between the thrill of exploration and adaptation versus the fear of death being ever at hand, largely involving our two main protagonists, Monsore and young Charlotte, who's out to see if her brilliant idiot of a brother has adventured in to the depths below. Yes, these two have to deal with a myriad of unknown settings, situations, and creatures, on top of their colleagues losing their marbles as the adventure goes on. That, and outright dying. In tone, the book is strangely both exhilarating yet gloomy. Great fun to marvel at, but rather weird and uncomfortable to experience.
There are also some interesting meta-themes covered, such as: what is man's natural state? Is reason and 'progress' the better-lived life, or is it more important to live in the moment? Another one: is it possible that the Earth is a super-organism, with the various creatures we view as separate species being more like cells and antibodies as part of an overall 'Gaia' collective?
More on these tremendously-talented creators and their works:
https://www.lambiek.net/artists/k/kerascoet.htm
https://www.lambiek.net/artists/v/vehlmann_fabien.htm