When the Digital and Real worlds are threatened by the Dark Ocean rising beyond its shores, Kari and the Destined take the fight into a Dark World bereft in turmoil. Deep in the soil, swamp, snow, sand, and seas rest secrets of a distant past that will upend the present and change the future. Can Kari, the All-Mother, restore the barriers between worlds, or plunge them in darkness?

A great, ringed-city between the Four Great Continents. It was the seat of the fifth and strongest Guardian, now dormant and imprisoned. Until one unlikely man and his pair of Gazimon set foot in that forbidden place, dragging the Digi-Destined into a war against the three Celestials, discovering darker secrets within the city's walls and deep beneath the frozen ground.