On point with the theme of dark: You are in a black hole trying to defeat a demonic deity before it kills everyone.
I go into that fight with 9 pizzas and about 120 coffees (revival potions, for those of you who have not played it). Coming out of that first try I have... 0 pizzas, and I reckon about 95 coffees. Easy mode, not necessarily difficult, but tedious. A word of warning! The Hydra... thing... was the hardest IMO. You have boiled killing multiple entities down to a fine art by then. Hard? Not really. Long? YES! Took me about 30 minutes to kill Akron. I mean, he does have a little more than 500k HP on easy mode, (making it have about 715K in any other mode).