Limbo is a place of the forgotten, where all outdated comic book characters go: the forgotten, the unpopular, the silly ones, those who no longer appeal to readers' tastes. It is where all objects and people lost to the revision of continuity end up.
One enters Limbo when they are forgotten, but once they leave, they never remember having been there. And if you stay, your own memory will soon fail you.
Seen for first time in Animal Man, the geography of the Limbo includes a library with only one book, an infinite book where all stories are being depicted.
When Superman, Ultraman, Overman, Captain Atom and Captain Marvel travelled through the multiverse, they found themselves stranded in Limbo. There they participated againts a shadow demons attack with the help of Limbo inhabitants.
In the map of the multiverse, limbo can be seen in several positions above the sphere of the gods.