The World Root was a massive tree root system that extended around the entire planet of Kwejian. To the Kwejian people, it symbolized their heart and the unbroken chain of their ancestors. The Ikhu Zhen ceremony took place there, during which a Kwejian boy would receive an amulet filled with sap from the World Root. It was destroyed along with the planet by the Dark Matter Anomaly in 3190. (DIS: "Kobayashi Maru")
While convincing Species 10-C to dismantle the DMA, Cleveland Booker told them about the World Root and how it had connected all of his people. (DIS: "Coming Home")
Two cuttings from the World Root were deposited at the Eternal Gallery and Archive. Much later, following Kwejian's destruction, they were moved to a place of honor as per the Archive's sacred duty to preserve the memory of lost cultures, though the archivists were unsure exactly what they were. In 3191, Hy'Rell showed the cuttings to Booker for identification, and allowed him to take them as one of the last living Kwejian. In return, she asked only that he return one day and tell the Archive what had become of them for their records. (DIS: "Labyrinths")
Booker subsequently planted the World Root cuttings on Sanctuary Four. Decades later, they had grown into a massive tree. (DIS: "Life, Itself")