Artifact crossbow Thunderclap, which fires either lightning or lightning-enhances the crossbow bolts it fires, and you can invoke it to create more bolts.

If you pray while there are hostile monsters near you, your god may decide to answer the prayer by frying all the monsters around you with lightning (sparing pets and peacefuls). This would work best when there are a bunch of hostiles right near you but none a medium distance away. Possibly it should be suppressed when your HP is low, but then again restoring your health while leaving you surrounded by monsters often doesn’t give you high odds of surviving.

The hero is not credited with killing the monsters, and gains no experience or penalties.

Lightning doesn’t pass through iron bars. Instead, it electrifies the bars and any bars contiguously connected to them (possibly within some range), causing any creature occupying one of the electrified iron bars squares to be zapped as if the lightning ray hit them.

Divine lightning (a god smiting you, particularly Moloch when you attack his high priest) should ignore reflection; it’s a “wide-angle” blast of lightning. Maybe this should apply to the lightning monster spell too. The high priest of Moloch should also be shock resistant.

In variants with the Wands Balance Patch, or otherwise have multiple levels of lightning power (Skilled lightning spell or something), lightning should chain into other monsters near the first thing it hits. Chain lightning can still be reflected. The jumps are made in random directions, so hitting a monster close to you may cause it to chain back into you.

The proper way to make late-game elemental damage matter is to give late-game enemies elemental attacks with large enough damage to matter, which don’t care about reflection.

Storm giants have active and passive lightning attacks. Not sure why they don’t actually have anything to do with shock currently.

Lightning spells:

• The most common suggestion is for a level 5 attack spell that creates a lightning bolt, implemented as a simple ray. Possibly, it causes an electrical explosion on the first target it hits if cast at Skilled and Expert.
• Alternatively, a spell of lightning bolt could be a melee range spell that deals heavy shock damage.
• Chain lightning is a spell that forks off and hits adjacent targets in a breadth-first search (see here for how it might work). Possibly, the lightning bolts can only chain off at 135 or 180 degree angles (maybe 90, too). Chain lightning can still be reflected, but becomes a straight ray.
• Lightning storm, which causes an electrical explosion centered on every monster in your line of sight (possibly with a decreasing chance of doing so as it gets further from you). Or if this is too overpowered, just strike these monsters with an individual lightning bolt that does not cause an explosion.

Invoking Mjollnir allows you to cast a bolt of lightning as if from a lightning wand.

Expert use of the wand of lightning doesn’t create a lightning explosion on the first target it hits; it creates chain lightning instead that may hit adjacent targets.