Due to some unspecified catastrophic disaster ( That was probably the fault of the planet's inhabitants, if you think about it. ), the planet of Ester has been torn apart inside out! All that remains is the somehow magical World Tree of Ester, the only thing holding the last chunk of Ester intact, Atmosphere and all, against the spontaneous fires that are an after effect of the cataclysm. Unfortunately the forces behind the disaster are far from finished, and the World Tree must create saplings of itself by taking the water in whatever's left of the atmosphere, and THROWING INTO SPACE in the vain hope that they might land on a habitable chunk of rock. Hey, it's sentient tree. Who are we to judge?