There is a huge variety to what you might see from run to run and region to region.
As you progress through the dungeon you'll find equipment that can be enchanted, upgraded, and augmented as you outfit your hero. Over 250 items including equipment, consumables, and items crafted via alchemy. Shattered Pixel Dungeon 9 optional challenges and over 100 achievements for completionists. Battle hostile wildlife in the sewers and caves, mad thieves and guards in the prison, occult servants in the fallen dwarven city, and maybe something even worse further down.