World 13 (Dr. Mario World)
World 13 is an underground crystal cavern world resembling Tilted Tunnel from New Super Mario Bros. U in Dr. Mario World. The first area is available as of 1 AM PT on Mar. 5, 2020, while the second area, challenge stages and special stage are available as of 2 AM PT on Mar. 19, 2020.
When an area is cleared, Bony Beetles, Bone Goombas, and Swoops appear. The viruses featured in the regular stages are red, yellow and blue, with the exception of one stage, which has green viruses in addition to blue.
Stage names in bold red text are labelled as hard stages in the game.