Somewhat related to this topic is that of beasts capable of traversing both the [[Physical plane|Physical]] and Ethereal plane at the same time. One example of this is the demon called simply: "the [[{{iw|Hidden]]Hidden}} ". Used by [[Diablo]] when he corrupted [[Tristram]], the demon is capable of phasing in and out of the Physical and Ethereal plane, essentially walking the line between them. This creature will travel on the Ethereal realm until someone is vulnerable to ambush. If wounded, he can phase back into the Ethereal plane to [[heal]] his wounds.