‘Oasis’ is a playable, AI-generated version of ‘Minecraft’ that has been trained on millions of hours of game footage, and has created a hallucination-filled nightmare that echoes digital folklore.

The wildly popular game “Minecraft” is a lot like its creator, Markus “Notch” Persson: modest in style and origin and apparently still true to its roots despite phenomenal success. In their new book ...