Chain Lightning

Version 0.30: This article may not be up to date for the latest stable release of Crawl.

Chain Lightning
Level	9
School1	Air
School2	Conjuration
Source(s)	Book of Annihilations
Casting noise	25
Spell noise	10
Power Cap	200
Flags	Area

Releases a massive electrical discharge that arcs to the creature nearest the caster and then outward from it. The further it travels, the less damage it does. Secondary arcs have limited range and do little damage to the caster. The spell's damage partially bypasses armour and resistance to electricity. “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -traditionally attributed to Samuel Clemens.

Spell Details
Damage Formula	3d(2*Power/3) electricity
Max Damage	3d133
Max Power	200
Range	LOS
Targeting	LOS
To-hit	Automatic
Special	Partially irresistible

Chain Lightning is a devastating, but unwieldy level 9 Conjurations/Air Magic spell which unleashes a massive surge of electricity. It has a tendency to damage the caster, but they receive a great reduction in damage.

Useful Info

There is no way to aim Chain Lightning. When cast, it creates an "arc" of lightning, which strikes the nearest valid target (randomly chosen if multiple targets are equally close), then creates another arc. Each consecutive arc will hit anything within 3 squares of any previous target, that 1. hasn't been hit before, and 2. is in LOS. This continues until there are no valid targets.

Each arc deals two-thirds the damage of the previous arc. The initial strike deals full damage only at point-blank range, with the damage reduced by one arc's worth from range 2 to 4, and two arcs' worth from range 5 to 7. Half of the spell's damage is irresistible, and only half of the target's AC applies.

The caster can be hit by their own spell, but takes only 1/6 damage. With rElec, this damage is almost negligible, and even without rElec it doesn't do much (expect 10-20). The caster's allies are not protected from this spell (unless they are protected from all damage, such as Hepliaklqana ancestor or Fedhas plants).

Strategy

Chain Lightning deals incredible damage against single targets, without the delays of Maxwell's Capacitive Coupling. It also works nicely as an area-of-effect spell: arcs will hit targets, close or far, for decent damage, and it doesn't get weaker when hitting more targets. The optimal cast is when against 1 (or more) adjacent opponents, with a dense pack of monsters nearby.

At moderate spell power, Chain Lightning can take out powerful uniques in 2-3 castings. At max spell power, it becomes one of the most potent damage sources in the game, bolstered by it partially ignoring electricity resistance.

However, as a level 9 spell, its tough to cast for a typical 3 rune character. Worshippers of Vehumet and/or those with high aptitude in magic (Tengu especially) are best suited to use this spell, while other characters can settle for spells like Plasma Beam or Iron Shot.

Tips & Tricks

• Wielding a staff of air provides a significant boost to damage, and grants you resistance to the self-damage; definitely consider wielding one if you can find it.
• Plants, fungi, and bushes are not valid targets for Chain Lightning, so they cannot extend the range of the spell.
• Followers of Beogh, Yredelemnul, or any other character that makes heavy use of allies should use extreme caution before casting Chain Lightning. You are almost guaranteed to injure or kill your allies in the process.

Monster Version

Some monsters can cast Chain Lightning which functions identically to the player version. Watch out for Nikola's 264 damage, if you have no rElec and are adjacent to him.

The following enemies cast Chain Lightning:

• @ Nikola (3d45 damage)

The following enemies may be able to cast Chain Lightning, depending on their spell set:

• & Pandemonium lord (3.4% chance)

Gallery

• 

  Example of Chain Lightning targeting.
  Arcs go from green (66%) -> yellow (44%) -> orange (29%).
  (Note that the initial arc may also hit the fire giants first.)

History

• The spell was reworked in 0.27. Prior to this version, Chain Lightning was a Level 8 Conjurations/Air spell that went from target to target, dealing reduced damage each time. Also, the spell's damage couldn't partially bypass resistance to electricity.
• Chain Lightning was added in 0.1, replacing Orb of Electrocution.