Rift Worlds are a little understood class of planet.
Rift Worlds have a multitude of unusual traits. First, they all have a strange shape, be it cubic, recursive sphere or toroid. Second, they all have at least three Portal Rifts that link them to other Rift Worlds. Third, they all have a very high Thaumic Energy content. Fourth, they all are inhabited by complex carbon based life. There is much scientific, theological and filmographic culation behind them. One theory is that they are an artificial consruct, another is that they are points where this universe and the dimension that is the source of all Thaumic Energy intersect! One fringe idea is that they are older than the universe.