At level 66, you can train for this spell regardless of your build. The tooltip is markedly uninformative: “Creates a shadowy fiend to attack the target. Caster receives mana when the Shadowfiend does damage. Lasts 15 sec.” Casting it needs 6% of your base mana (gasp), it’s an instant cast, and there’s a 5 minute cooldown.
Here’s the basic deal. If you have absolutely nothing boosting it, it’ll do approximately 1100 damage and will return about 2750 mana, all over 15 seconds.
A bit more broadly stated: if you have nothing boosting it, the fiend can hit every 1.5 seconds for approximately 110 damage per hit. Every point of damage returns 2.5 mana.
Oh – and since it is considered a pet, YOU don’t get aggro from the cast. Stop, reread, chortle, continue….
What boosts it?
Any enhancement of spell- or shadow-damage. Shadowweaving, spellpower enchants, CoS from your friendly warlock, shadowform… all boost the damage. +damage gear (and spellpower) have a coefficient of 57% because it’s an instant. Percentage boosts are straightforward. Yes, this means shadow-spec gets more out of it than Disc or Holy, but even those two can have some impact. Also…
Anything that increases your fiend’s speed of attack will boost the overall damage. Watch for your shaman popping bloodlust or heroism — a 30% boost in speed means you expect 13 instead of 10 attacks over the spell duration for about a 30% increase in damage and mana. Finally…
Spell Crit gear is worth noting. The attack uses melee, not spell, combat tables (though the crit portion uses your spell crit). Thus every crit increases damage by double instead of 50%. That 110 becomes 220 returning 550 mana.
What hampers your spell?
It can be dodged. It can be parried. It can be blocked. It’s considered a MELEE ATTACK (except it uses shadow damage). (Actually, each “attack” can be dodged, parried or blocked.) But when it comes time for damage mitigation, armor has no effect. Shadow resistance does ( with counter-mitigated by penetration).
So… how do I use this thing.
Most frequently, it’s used for boss fights. My general guide for timing its use is based on two factors – the expected amount of mana to be returned, and the expected time of the fight.
I can estimate mana return by seeing what my normal SW:D damage is in comparison to “the book’s” unenhanced value and applying that to the Fiend. Since I assume I’m going to miss once and crit once I can use that number. (One miss, 8 normals, one double is 10.)
As an example: Say I’m getting about double SW:P’s damage. That makes F’s damage ~2220. So my normal expected mana return is ~5550. Which means (for me) that I don’t waste the mana if I wait till I’m below half. However…
If I expect the fight to last long enough to pass the cooldown, I may trigger the fiend early. Popping it when I’m only down by, say, a quarter means I waste 2500 or so mana now. But five minutes from now, when That Boss is shifting to a heavier attack, I’ve got ANOTHER mana-pot-equivalent available.
Before I go, I want to mention the fact that your fiend is not just for mana regen on bosses. Consider the following situations:
My party’s pulled a group of four. One’s dead, one’s in combat, two are CC’d, and we get a single pat. If I pop my shadowfiend at this mob, I: a) bought 15 seconds of time for the party; b) knocked down the mob’s health by ~2K; c) regained ~5K mana; and d) picked up no additional threat leaving the tank PLENTY of room to grab it’s attention. (note – I can toss it at an add in a boss fight too. And since adds don’t usually have the resistances bosses do, I’m probably going to get MORE mana out of it.)
I’m soloing, and I’ve pulled too much heat. I PScreamed preparatory to running, but one of the mobs resisted. I can pop the pet and start running (remembering to key the fiend to Defensive), and I’ve got 15 seconds of time. In slight variation, I can also send my fiend after that mob that fled right down the path I intend to use to escape.
I think the fiend is a woefully underused beast as too many priests have never used a pet, and haven’t realized the capabilities inherent in the spell. Hopefully, you will not be one of those priests – and the Fiend shall be a constant companion.