The nine planets, or the Portallip, were the first known planets inhabited by intelligent life. In the second age of string, Xeric took a turn in the making of things, and bestowed a system of intergalactic portals.
The Portallip are distinct from other inhabited planets and moons by virtue of having a portal. The portal provides a gateway to another planet depending on the alignment of the planet's moon or moons. A kind of lunacy.
Indeed it's a two part kind of lunacy to enter a portal, for while it is known that a being will survive the hop to another planet, there is no guarantee what kind of lifeform it will reincarnate as. Sometimes no change and sometimes a completely different life form.