A ley line is a naturally occurring stream of mana across the earth’s surface. Ley lines allow the effects of magic to be amplified, so magicians and magical creatures often take advantage of the abundance of mana. For example, creatures will create their nests near them, and trains that carry magicians between domains run along ley lines.
In rare cases, ley lines can be manipulated. One example is the funneling of ley lines to create and sustain New Salem. Another example is the distortion of ley lines around Gertrude Rosenfeld’s domain to make it visible to the naked eye.