It’s typical to think that all the malignant arcane monsters made in this world are birthed by wizards, sorcerers, and their ilk. That the colleges and towers of Dungeon World are womb to every bleak experiment. There are mistakes made in the depths of the earth, too. These ones, the derro, are the mistakes of a long-forgotten dwarven alchemist. The derro don’t forget, though. Twisted and hateful, the derro can be spotted by their swollen skulls, brain-matter grown too large. They do not speak except in thoughts to one another and plot in the silent dark to extract sweetest revenge—that of the created on the creator. Instinct: To replace dwarves

• Fill a mind with foreign thoughts
• Take control of a beast’s mind