The re-opened connections between Earth and Kur are at the heart of humankind's troubles. The Interworld Tree connected nine worlds at apogee of the Lifeweaver's civilization. Later they allowed the Kurians and their forces in in the first place, and occasionally are the portals for more of the same to arrive. How they are opened in the first place is a mystery science has not yet fathomed, we only know it involves the use of a great deal of vital aura, in other words, suffering and death. There are three well known gates in North America: the largest is in Virginia, the oldest in Louisiana (unless you count the now almost three hundred year old one in Haiti), and the most frequently used one is near the California/Nevada border, as the climate in the Southwest and Mexico is very much to the Kurians' taste.
Not much is known of Kur itself. It is a dark, gloomy planet of heavy clouds where most of the gardens are underground. Tales tell of omnipresent red skies, something the Kurians are still trying to achieve on Earth, and an underground world millions of years old dating back to the Pre-Entities (indeed, some Kurians seem to be searching deep within the bowels of our own Earth for Pre-Entity tunnels, perhaps in the hope of finding lost gates to the rest of the Interworld Tree).
Thousands of years ago humans were sometimes invited to travel the Interworld tree. They saw Ero, the home planet of the Lifeweavers, by all accounts an idyllic, garden and forest filled world of great beauty.
Descriptions of Mes fill a few legends: it is a world of towering spires of rock inhabited by winged men who perhaps formed the basis for visions of angels.
There is also Rulallah (RUL-al-leh), a planet of howling winds, storms and a hard life within stout stone walls.
Korkh may have many climates, but the only one we know of is vast, deep, rugged jungle where the grey-skinned, apelike grogs were developed under triple canopies of vegetation.
The Lifeweavers shut the doors between worlds to halt the Kurian cancer. But if they created new doors to Earth, how many others were constructed elsewhere?