Creates a shadowy fiend to attack the target. Caster receives 5% mana when the Shadowfiend attacks. Damage taken by area of effect attacks is reduced. Lasts 15 sec.
the Shadowfiend is the only pet a Priest can control. It summons a combat Shadowfiend to fight with the priest for 15 seconds dealing shadow damage. Each time the pet lands an attack, the caster priest gains 5% of mana. A pet action bar appears for the priest to command and control its spells.
The mana gained from Shadowfiends' attack is 5% of the caster's maximum mana.
Without shadow damage bonus, the Shadowfiends' hits deal an average of 180 damage to an equal level mob without shadow resistance. Its average damage per attack, however, can be significantly lower due to melee damage mitigation.
The Shadowfiends' attacks are shadow damage and can be partially resisted but follow normal melee damage rules, therefore being capable of critical strikes, but also susceptible to misses, parries, dodges and glancing blows. This reduces the damage output of Shadowfiends considerably on higher level mobs (especially in raid encounters) and in PvP versus classes with high melee mitigation or shadow resistance.
Shadowfiends deal shadow damage. Therefore, their damage can be increased by debuffs on the shadowfiends' target that increase shadow damage taken (e.g. "Curse of Elements") resulting in greater damage. Note that Shadow Weaving will not affect shadowfiend damage.
The Shadowfiend grants up to 11 hits per use, although this number is usually 10. Its attack speed is 1.5 and it has a 15 second duration. It is rare but possible for it to get one final attack as it expires if it spawned adjacent to your target.
The Shadowfiend receives 357-393% of your shadow damage bonus over the 15 second duration depending on 10 to 11 attacks, or 35.7% per hit for 10 hits.
The patch 2.1 implemented a normal petbar for the priest to further help the priest control his/her shadowfiend. The bar functions as a normal petbar, with Attack/Stay/Follow and all three modes of Passive/Defensive/Aggressive. The shadowfiend will spawn next to the priest in Defensive mode with [Shadowcrawl] on autocast, and it will immediately attack the priest's current target. Despite Shadowcrawl being on autocast, it will almost never use the spell on its own.
If the Shadowfiend's target dies, it may pick another target at random, or it may simply return to the priest's side, both of which will cause it to waste time and you forfeit valuable mana. Try to use the Shadowfiend on targets that will not die or otherwise become unattackable before it despawns.
Shadowfiend takes on the buff of Bloodlust/Heroism if it is active when [Bloodlust]/[Heroism] is cast, and it will hit the mob faster and return more mana. When circumstances are conductive, using Shadowfiend shortly before Bloodlust/Heroism can yield a good deal of extra mana.
A macro to have the Shadowfiend use [Shadowcrawl] on your current target immediately after being summoned can result in about an extra 560 damage over its duration in high-end raid gear. Additionally, macros bound to your other spells to have the shadowfiend re-cast Shadowcrawl can yield another 950 damage. With the talented 3 minute cooldown, these macros come out to a DPS gain of 8.4. Every little bit helps.
Patch changes
Patch 3.3.0 (2009-12-08): [Avoidance] (passive): Now reduces the damage your pet takes from area-of-effect damage by 90%, but no longer applies to area-of-effect damage caused by other players.
Patch 3.1.0 (2009-04-14): Health scaling increased. Now receives 30% of the master's spell power. Mana return increased to 5%, up from 4%. The Shadowfiend now returns mana when its melee attacks land, rather than when it deals damage. Movement speed normalized to player movement speed. Tooltip revised.
[Mental Agility], 
[Shadow Reach], 
[Veiled Shadows]
90
[Shadowcrawl] on autocast, and it will immediately attack the priest's current target. Despite Shadowcrawl being on autocast, it will almost never use the spell on its own.
