Upon casting this spell, the wizard releases a powerful stroke of electrical energy that inflicts 1d6 points of damage per level of the spellcaster (maximum damage of 10d6) to each creature within its area of effect. A successful saving throw vs. spell reduces this damage to half (round fractions down).
The bolt begins at a range and height decided by the caster and streaks outward in a direct line from the casting wizard (e.g., if a 40-foot bolt was started at 180 feet from the wizard, the far end of bolt would reach 220 feet (180 + 40).
The lightning bolt may set fire to combustibles, sunder wooden doors, splinter up to 1/2 foot thickness of stone, and melt metals with a low melting point (lead, gold, copper, silver, bronze).
Saving throws must be rolled for objects that withstand the full force of a stroke (see the fireball spell). If the damage caused to an interposing barrier shatters or breaks through it (i.e., the saving throw fails), the bolt continues. A bolt can breach one inch of wood or 1/2 inch of stone per caster level up to a maximum of one foot of wood or 1/2 foot of stone.
The lightning bolt's area of effect is chosen by the spellcaster: either a forked bolt 10 feet wide and 40 feet long or a single bolt five feet wide and 80 feet long. If a bolt cannot reach its full length, because of an unyielding barrier (such as a stone wall), the lightning bolt rebounds from the barrier toward its caster, ending only when it reaches its full length.
Example: An 80-foot-long stroke is begun at a range of 40 feet, but it hits a stone wall at 50 feet. The bolt travels 10 feet, hits the wall, and rebounds for 70 feet back toward its creator (who is only 50 feet from the wall, and so is caught in his own lightning bolt!).
The DM might allow reflecting bolts. When this type of lightning bolt strikes a solid surface, the bolt reflects from the surface at an angle equal to the angle of incidence (like light off a mirror). A creature crossed more than once by the bolt must roll a saving throw for every time it is crossed, but it still suffers either full damage (if one saving throw is missed) or half damage (if all saving throws are made).
The material components of the spell are a bit of fur and an amber, crystal, or glass rod.