Complex sentence: The Hellfire dungeons are populated with enemies that do not appear in the main Diablo quest, however, and the difficulty of Hellfire dungeon floors 1-8 mirror those of levels 9-16 of the main Diablo quest, requiring experienced characters to explore.
Split into simpler sentences: The Hellfire dungeons are populated with new enemies that do not appear in the main Diablo quest, however. The difficulty of Hellfire dungeon floors 1-8 mirror those of levels 9-16 of the main Diablo quest, requiring experienced characters to explore.