Little of the Outsiders or “Walkers” is known. They may be the most powerful of the Demons, or stranger and even more powerful entities akin to Lovecraftian Great Old Ones. It takes wizards centuries to develop defenses against them and magic apparently has little effect upon them. They can be defeated by, among others, the powers of the Knights of the Cross. However, Outsiders cannot actually be killed, only damaged sufficiently as to require long years to recover; this has been confirmed in numerous cases. There are rumors that some may possess a special power due to the timing of his birth, that could potentially give them the power to actually kill Outsiders, a deed believed to be impossible at this point.

Wizards are terrified of the Outsiders and of their power; however, as only mortal magic can summon an Outsider (neither vampires nor faeries can do it), the temptation to gain power can be irresistible, and the Seventh Law against Outsider summoning is unique among the Laws in that a single Senior Council member is assigned to enforce it full-time. (Though The Blackstaff can summon an Outsider, as part of his general exemption.) Their internal organization is only sketchily understood, but they appear to have a caste system which includes empires and knights. It is as yet unknown whether they are the “Lords of the Outer Night” rumored as supporting the Red Court, but Outsiders have aided the Red Court in the war since.