Lightning Shield

From WoWWiki

Lightning Shield
Lightning Shield Instant cast The caster is surrounded by 3 balls of lightning. When a spell, melee or ranged attack hits the caster, the attacker will be struck for X Nature damage. This expends one lightning ball. Only one ball will fire every few seconds. Lasts 10 min. Only one Elemental Shield can be active on the Shaman at any one time.
Usable by
Class	Shaman
Properties
Type	Offensive
School	Nature
Cooldown	None/Global Cooldown
Talents
Improvement talents	Improved Shields, Static Shock
Other information
Ranks	11
Related buff
Magic Lightning Shield Causes X Nature damage to attacker on hit. Duration: 10 min. or 3 charges

Lightning Shield is a nature-based buff. When getting attacked, it does direct damage to the attacker. It can only proc every few seconds and has three charges.

Rank table

Rank	Level	Damage per Orb	Cost
1	8	13	90
2	16	29	16 20
3	24	54	31 50
4	32	80	72
5	40	114	1 8
6	48	154	1 98
7	56	198	2 70
8	63	232	3 78
9	70	287	7 92
10	75	325	??
11	80	380	??

Notes

Being an elemental shield, Lightning Shield cannot be used at the same time as Earth Shield or Water Shield. It is however possible to use Water Shield or Lightning Shield on yourself while Earth Shield is up on another target.
It uses the lightning animation instead of the normal nature animation.
Each charge receives 33% of spell damage.
The damage caused is considered direct damage, though it cannot crit.
Each charge will consume a charge of the Zandalarian Hero Charm's Unstable Power aura.

Troll Shaman casting an Lightning Shield in Badlands.

Improvements

Improved Shields increases the damage done by Lightning Shield by 15%.

Static Shock increases the number of charges by 6, and gives a chance on melee attacks to hit the target with a Lightning Shield orb.

Glyph of Lightning Shield increases its damage by 20%.

The Enhancement Shaman Tier 7 2-piece set bonus (provided by Heroes' Earthshatter Battlegear and Valorous Earthshatter Battlegear) increases Lightning Shield damage by 10%, including damage from Lightning Shield orbs consumed by Static Shock.

Tips and tactics

Lightning Shield is a good alternative to Water Shield for solo play or PvP, especially if mana is not a problem (either because you have enough mana anyway or because you expect fights to be quick).