In Christian tradition, demons are fallen angels (Revelation 12:7-9), and have the same characteristics as their good angel counterparts: spiritual, immutable and immortal. Demons are not omniscient, but each one has a specific knowledge (sometimes on more than one subject). Their power is limited to that which God allows, so they are not omnipotent. No reference has been made about omnipresence, so it is as yet unclear if they can be in different places at the same time, but according to the tradition of the medieval witches' Sabbath, two conclusions can be reached: either the Devil can be in different places at the same time, or he sends an emissary in his name.