Ley lines are powerful currents of arcane energy found throughout the world in varying strengths. An arcane caster can safely tap into a line if they take appropriate precautions in the form of a special ritual. Few bother, however, as the time and effort required to enact such a ritual, as well as the expensive materials required, is not worth the temporary power boost the tap provides.
Chaos sorcerers* are individuals who have learned to harness a small amount of this power, imposing order upon it with iron discipline and willpower. This can have unpredictable and dangerous effects, and most students of arcane magic see the practice as the province of fools and madmen.
*Sorcerers with the Wild Magic origin