Limbo is a place between all the Domains and the Dream realm. Dream Guides are, as opposed to in Dreams, not able to influence the environments, even though the environment will develop itself and sometimes change in inexplicable ways when you’re not looking.
It is the realm where Dream Guides land when they are chosen, and the place where they have their home for as long as they stay. To prevent their home from changing behind their back, it is protocol to always have at least five Dream Guides stay in camp and survey. Though in a practical sense, this protocol has never been needed to be enforced, because Dream Guides have never had to leave the camp in large numbers.
Unfortunately, Limbo has become plagued by creatures they call the Undying. These huge skeletal creatures attack the Dream Guides and wreak havoc in Limbo, for no other apparent reason than to see them gone.