Power Word: Shield

Power Word: Shield (abbr. PW:S) is a defensive priest Power Word available at level 6. It creates a protective shield around a friendly target which absorbs a set amount of damage. Power Word: Shield also gives the target the Weakened Soul debuff, preventing the target from being shielded again for 15 seconds.

While Power Word: Shield is a valuable spell for any priest, Discipline priests have the opportunity to improve it far beyond its base effect, using it to restore mana, grant haste and even reflect damage back upon the attacker. Power Word: Shield is undoubtedly one of the signature spells of the Discipline priest, protecting the target with a powerful shield that can seem unbreakable.

Talents and spells
Discipline Mastery: Discipline Tree Talents: Holy Tree Talents:
 * Shield Discipline increases the potency of all your damage absorption spells by 20%. Each point of Mastery increases the potency of absorbs by an additional 2.5%.
 * Improved Power Word: Shield increases the amount of damage absorbed by 10/20%.
 * Twin Disciplines increases all your Shadow and Holy spell damage and healing by 2/4/6%.
 * Mental Agility reduces the mana cost of all your instant cast spells by 4/7/10%.
 * Soul Warding reduces the cooldown of your Power Word: Shield ability by 1/2 sec.
 * Renewed Hope increases the critical effect chance of your Flash Heal, Greater Heal, Heal and Penance (Heal) on targets afflicted by the Weakened Soul effect, or blessed with your Grace effect.
 * Rapture: When your Power Word: Shield is completely absorbed or dispelled you are instantly energized with 2/4/6% of your total mana. This effect can only occur once every 12 seconds.
 * Borrowed Time grants 7/14% spell haste for your next spell after casting Power Word: Shield.
 * Reflective Shield causes 22/45% of the damage you absorb with Power Word: Shield to reflect back at the attacker. This damage causes no threat. Please note, this talent will only reflect damage that YOU absorb using PW:S. It will not reflect damage absorbed by any PW:S you have cast upon others.
 * Strength of Soul: When you heal a target with Flash Heal, Greater Heal or Heal, you reduce the duration of any Weakened Soul debuff on the target by 2/4 sec. While this talent does not improve Power Word: Shield itself, multiple procs of this effect may effectively reduce the cooldown of your PW:S upon that target considerably.
 * Spiritual Healing (Holy specialisation ability) increases healing by 15%.
 * Body and Soul: When you cast Power Word: Shield, you increase the target's movement speed by 30/60% for 4 sec.

Items

 * Tier 8, set: Conqueror's Sanctification Regalia or set: Valorous Sanctification Regalia: Four piece set bonus grants 250 spell power for 5 seconds upon casting Power Word: Shield.
 * The All-Seeing Eye of Zuldazar: On equip, increases the amount of damage absorbed by Power Word: Shield by 35.

Tips and tactics

 * Casting it before combat does not cause any threat and reduces the time until the target can be shielded again.
 * A major disadvantage of the shield is that it is a limited form of damage mitigation, not a true healing spell, and so may wear off without having been of any use. With a limited duration of 15 seconds, priests must choose their timing in order to ensure mana is not wasted casting the spell to little or no advantage.
 * Mana efficiency of Power Word: Shield is typically predicated upon the shield being fully absorbed. In practice, with only a 15 second window for this to occur, in many situations the shield will fade without being completely absorbed. In these cases the spell can be considered to be far less mana efficient.
 * Power Word: Shield upon enemy targets can be dispelled with Dispel Magic, Mass Dispel and similar spells.
 * Paladins want to be healed rather than shielded, even though they are perfectly capable of using Divine Plea and Judgement of Wisdom. They receive mana from heals, but not from Power Word: Shield. Paladin tanks have tiny mana pools and rely on healing or will go oom.
 * The effectiveness of Power Word: Shield is not altered by Mortal Strike and similar healing-reducing debuffs; in these situations it can sometimes be more effective to shield a tank first, rather than spam heals right away.
 * This is useful for casters who are receiving damage, as it prevents spell interruption from damage, especially while they are channeling, and even the priest himself can benefit from this (especially in solo combat).
 * In PvP, this spell can be a huge boon to bestow on Rogues and Feral Druids. Any damage taken will unstealth a character. However, if you Power Word: Shield a Rogue, AoE damage that doesn't get through the shield is absorbed, which greatly increases the difficulty of finding a Rogue by laying down an AoE. Power Word: Shield will also absorb the damage from DoT's, allowing DoT'd Rogues to Vanish safely. Just know that if the AoE or DoT damage is greater than the shield will take, then the actual character will take damage and stealth will become undone.
 * Power Word: Shield can also be seen as a way of pushing a tank's health beyond its normal limit. It is effective to Power Word: Shield before major attacks that will destroy the shield in one blow. Using it before Patchwerk's Hateful Strike or similar devastating attacks reduces the chance that a tank will die to a possible critical hit after such an attack.
 * When glyphed with Glyph of Power Word: Shield, priests may wish to allow targets to take a small amount of damage before shielding them, in order to benefit from the additional 20% direct heal.
 * There was a time when Power Word: Shield would only be used in case of emergency because of its large mana cost and cooldown. Now it is a mainstay of healing for priests and is actually one of their most mana efficient heals.
 * The Weakened Soul debuff can be shortened to 13 seconds with the 4 piece bonus from Gladiator's Investiture.

Bugs

 * The bonus given by Twin Disciplines do not apply correctly to the amount absorbed by the shield; the bonuses are added instead of multiplied. Thus, when fully talented, the size of the shield is multiplied by 1.09 rather than 1.092. (4% & 5% = 1.04*1.05 = 1.092)
 * Glyph of Power Word: Shield does not take into account the bonus from Improved Power Word: Shield when calculating the healing amount.
 * The amount healed by Glyph of Power Word: Shield is increased by any talents or effects the target has that increase healing done. For example, if the effect is used on a Restoration Shaman, the heal will be increased by 10% because of Purification.

Formula
Formula for calculating Power Word: Shield's total absorption amount, as of Patch 4.1:

(8136 + (0.87 * SP) * SD * SH * IMP * TD)


 * SP is your Spell Power.
 * SD is the bonus granted by the Discipline mastery Shield Discipline, eg 1.325 (5 points of mastery + base 20% buff = 32.5% buff). This is only available to Discipline priests.
 * SH is the bonus granted by the Holy specialization Spiritual Healing. All Holy priests have this, and it is always 1.15 (15% buff).
 * IMP is the bonus granted by Improved Power Word: Shield - rank 1 = 1.1, rank 2 = 1.2. Not talented = 1.
 * TD is the bonus granted by Twin Disciplines - rank 1 = 1.02, rank 2 = 1.04, rank 3 = 1.06. Not talented = 1.

Example: a rather modest Discipline priest with 3600 Spell Power, 5 points of Mastery and with both Improved Power Word: Shield and Twin Disciplines fully talented.

(8136 + (0.87 * 3600) * 1.325 * 1 * 1.2 * 1.06) = 18991

It should be noted here that PW:S absorb effects apply after ''damage reduction effects. This means that while the amount absorbed here is 18991 the character will most likely take far more than 18991 damage before the shield is completely absorbed.''