In TFL, chain lightning was something (a bug) a highly skilled player could control. Basically it was a combination of a ctrl-click on the ground then a very fast click on a distant enemy unit. Done correctly the lightning bolt would then travel the huge distance to the enemy unit.
"Making Fetch lightning go further than usual by way of a flaw in the Myth engine. Often referred to as "CL." This bug was eliminated in Myth: TFL, it doesn't exist in Myth II Generally considered Illegal during competitive gameplay.