Ley line

Great lines of power, known as ley lines, crisscross the lands of Azeroth. These lines of magic are often harnessed for mighty magical purposes, from the creation of moonwells to (some say) the powerful glowing dome of Dalaran and for the portal spells created by Mages. Ley lines exist all over Azeroth, and are sources of deep and natural magic.

Overview
Across the face of the world there flow lines of power - patterns of magical energy that carry vitality of the lands of Azeroth through them, like blood vessels in a creature. These lines of power are recognized subtly by every culture; the races of Azeroth identify them as those places sacred to the Light, the chosen locations of moonwells, haunted places where the power of death has tainted the flow of energy, and natural sites overflowing with elemental power that are sacred to shamans. Most cultures, however, only really focus on those places where the lines converge and meet, seeking to tap the most power from them. Those who seek to understand and master runic power understand that the convergences are not the only important part of this power - the patterns formed by the lines themselves are important as well. These patterns, which resemble letters in a strange alphabet, are called runes.

There are lines of power that run across the land in a select few areas, but these are not the only lines - simply the most obvious. Inside of these thick and corded ropes of power, there are also tiny, web-thin lines that run between these great ley lines, connecting them in a vast net of pulsing, subtle power.

Those with great magical power and ley walkers seek out these sites.

A community which sits on top of a convergence of two or more lines of magical energy is called a "ley line nexus".

Azeroth
All ley lines on Azeroth lead to a location under Karazhan, and they were the source of much of Medivh's powers.

Kalimdor

 * The ley line pattern of Restoration can be found in the Moonglade in the Valley of Dulvarinn. The rune pattern derived from the ley lines increases resistance to poisons and diseases, and is able to heal wounds at double the normal rate.
 * The ley line pattern of Beast can be found in the Vale of Beasts in Ashenvale. The rune pattern derived from the ley line is the source of all the beast mark spells.
 * Stonetalon Mountains has two known ley line patterns. Mount Farview is the location of ley line pattern, the pattern of Awareness. The rune pattern which is derived from the ley line amplifies the senses of the caster.  Another ley line pattern can be found in the Great Maze, known as the Stone pattern. The rune pattern derived from the ley lines can be used to increase resilience of the caster.
 * The indigenous tauren created a camp south of Mirkfallon Lake, built upon ancient ley lines in the Stonetalon Mountains. It is perhaps due to these ley lines that the elementals are drawn to the area around the Charred Vale.
 * Near the windswept plains of Mulgore, there is a series of hot springs that house the ley lines that originate the healing pattern. The rune pattern derived from the ley lines doubles the natural healing rate of healing spells.

Eastern Kingdoms

 * On the Isle of Quel'Danas there is at least one ley line, it seems to be the power source of portals, bloodstones, and a naga statue's power.
 * Ley lines in Ghostlands are used by the Sentinel Spies to spy on Silvermoon.
 * There also seems to be a ley line in the Eversong Woods, which gives the three sanctums (North Sanctum, West Sanctum and the East Sanctum) their power.This Ley-Nexus is also mentioned in connection with the Sunwell.
 * A dormant ley line flows beneath Ambermill.
 * There exists also a ley line beneath the ruins of Dalaran, which gave the mages of Dalaran their powers.
 * The Great Bulwarks near Grim Batol is the location of the ley line pattern of shielding. The rune pattern derived form the ley lines allows casters to generate protective wards around themselves.
 * A ley line pattern that forms the basis for the motion pattern can be found in a series of intricate canyons in the Badlands, wherein all manner of fast moving creatures can be found. Those who move quickly within this area find their movement inexplicably increased. Casters who use the rune pattern derived from the ley lines are able to increase their speed.
 * Blackrock Spire is the site of the ley line pattern of Striking. The rune pattern derived from the ley lines increases the martial prowess of the casters.
 * The ley line pattern of Flame is found deep in the Searing Peak in Redridge Mountains. When the rune pattern derived form the ley lines is used by casters, it increases fire resistance.
 * One ley line pattern exists in the mountains surrounding the city of Stormwind, which causes the great winds from which the city received its name. The rune pattern derived from the ley lines allows casters to unfailingly predict the weather one day in advance.

Northrend

 * The ley line pattern of Frost, is found in Northrend, in a vale of terrible, biting cold that is said to be the source of all cold in Azeroth. The rune pattern derived from the pattern increases cold resistance.
 * The pattern of cold weather was located in the Temple of Winter, but it has ceased after Hodir was taken away.
 * Also in the Grizzly Hills there is a ley pattern runing through the Eastwind Shore.
 * There is also one in the Coldarra where Malygos is using the Nexus to channel all of Azeroth's ley energy through it and shoot it into the Nether. Some ley lines in Northrend were redirected by the blue Dragonswarm to Azure Dragonshrine. One of those lines flew trough the Moonrest Gardens.

Outland
Like Azeroth's leylines leads to a location under Karazhan, most of Outland's leylines lead to locations near the Black Temple.

Redirection
Despite being incredibly old and powerful, ley lines can be redirected. Malygos did this with some ley lines in Northrend, and the Sarcen Stone, created during the War of the Ancients was also able to do so.