This one aims to be a relatively straightforward guide for building a Hierophant character towards a mechanically multi-layered, vulnerability and debuff(Flee)-supported spellcaster archetype.
Be warned: this build requires you to pay attention to your cooldowns, your class resource and buffs constantly, so if you’re looking for a laid-back, autopilot-like experience, you might want to try something different.

Considering the complex nature of the class and the overwhelming amount of specifics in passive trees and items, some elements like single Passive point choices, or the Retinue Members’ own skilltrees are left out as I consider them to be fairly intuitive and not too hard to figure out.
The build uses interactions between passives and item abilities which are “Essential” to achieve free spellcasting, CD resets and vulnerability stacking, I’m going to mark them as such.
Other bonuses and enchants are considered “nice to have” to increase damage output, or left out from the build entirely as subjects of player optimization and tweaking.
I used a level 87 character, the build is able to handle level 10+ maps with a high damage output. Optional changes are mentioned in the sections below if you have problems with survival.
No Morality, Archeotech or Seasonal enchants are used in this build for easier accessibility (altough they may provide a superior alternative instead of certain Godlikes.)

- Armor: Hierophant Vestment (of Shattering-Ancient Relic) –“Essential” item, enchants are nice to have
Activating the armor skill is going to reset your spell cooldowns by your RM-s hits and apply General Vulnerability stacks exceptionally fast using the Blessing of Holy Fire spell. Helps with survival too.(Note: General Vulnerbility’s bonus stacks with Heat Vulnerability, so you have a max. stack size of 20 with both of them applied. )
-Mainhand V1: Aether Blade (Explode on kill Godlike-optional)- Nice to have item providing an extra spell slot and great movement. Can roll “Life Drain” and “Shield Drain” enchants, which are S- tier among survival enchants.
- Mainhand V2: Inferno Pistol : I enjoy using an Inferno pistol too, it’s basic attack is great for easy vulnerability apply, but it strips you from a spell slot. You should leave out the spell“Blessing of Recklessness” with this variant (not recommended on high levels)
- Offhand: Libram,(Chance on hit for guaranteed critical hits/ Hierophant spells apply Hallucination Godlike)- “Essential” item and nice to have godlike enchant.
I’m using Libram for the multiplicative spell damage bonus. The godlike enchant triggers quickly while the Blessing of Holy Fire spell is hitting enemies, allowing your Blessing of Carnage to strike with a guaranteed critical hit. (Preferably, an additional layer of overall high Crit chance helps to keep your damage reliably high in situations where you can’t make this work.)
Alternately- applying Hallucination with your spells is a really strong option too.
- Belt: Curio of Fear or Immolation or any else (“Heat vulnerability on causing Burn” or “increased Critical chance after using a Curio” Godlike enchant)- Using a Curio is “Essential”, curio type is optional, enchant is nice to have)
Having the “Enlightened Curios” passive, you will want to use your Curio item after every third spell cast to save your Devotion for your Armor skill.
- Innoculator (Champion and elite enemies have 15% chance to drop a Supply Charge secondary enchant)- enchant is almost “Essential”, easily obtainable through simple reroll. Consider using the “Mitigator” red component on higher levels.

Other items are up for the player to otpimize. I would suggest going after “chance to cause burn on heat hit”, “Critical chance”, “Critical Strength”(preferably you’re going to have around 35%+ crit chance), “Chance to add Heat vulnerablilty on heat dmg dealt” enchants. Neural Implant of Boiling is nice to have.

-19 or 20 on Judgement (19 if you don’t have enough Devoiton)
-10 on Purity ( 15 or 20 if you have trouble with survivability)
-20 on Serenity (Focused Spellcaster bonus is “Essential”)
(Note: Serenity's tier IV bonus have been greatly buffed in a recent patch)

-“Cull the Weak" for easy extra damage,
-“The Art of Crippling” for extra duration on your Crowd Control effects, -or -
-“Vanquisher of the Vile” for 50% extra suppression dmg- both synergize well with your other mechanics.
-“Devoted to the Cause” for spell dmg (works well with Vestment’s Armor skill’s CD reset, “Essential”)

you may use “Blessing of Saint Victorius” instead of a non-Essential perk on high levels if you have problems with survival.

Not everyone has psalms stacked up in their Casket. None of these are considered “Essential” mechanically, all the Doctrines and Psalms used in this build are for plain damage increase or vulnerability effectiveness. Not having them won’t stop you from being able to use the build, but you’re going to need them to achieve a high enough damage on high difficulties.

The ones I use are:
Psalms, Gems: Vulnerability effectiveness psalms (have 1 of these in every item you have a free slot in), Thunderbolt of Authority gems, HP gems in free slots.
Psalm-Doctrines: 2x +125% Heat damage doctrines, 1x +70% heat Damage doctrine,
1x +150% dmg bonus to AoE skills and -30% radius doctrine.

Field Surgery on Health tree, Enlightening Curios on Utility tree.(both are “Essential” passives)

Blessings tree, Critical Hits tree, Defense and Heat Attacks (Volatile Output excluded) trees maxed out are nice to have.

Optional: a few remaining points on Retinue Tactics or Movemet or Area Effects trees.

Equipped spells are considered “Essential” but you can consider using Conflagration instead of Blessing of Recklessnes on lower level maps.
Blessing of Holy Fire (for Vulnerability stacking, on-hit and Crit procs, good damage and RM heal),
Blessing of Carnage for nuke-like damage and further spell damage increase.
Blessing of Recklessness for Crowd Control (helps survival with applying “Flee” debuff)
-or-
Conflagration for increased damage output (effective on lower levels, but doesn’t scale too well on higher difficulties )

A Crowd control and heat focused item setup for the Retinue Members goes like this:

-Crusader with the perk: Spellbinder. Equipped with Heavy Flamer (applies “Flee” to your enemies, "Essential") , Assault Armour, Digital Weapons
-Assasin with the perk Retinue Commander. Equipped with Melta Gun, Fabricatus Armour, Rosarius Force Field
-Psyker with the Perk: Power from Anguish. Equipped with Pyrokinetic Staff (Knockback and heat vulnerability), Empyrean Armour, Personal Void Shield
-Battle Sister with the Perk: Void Siphon Systems. Equipped with Flamer (applies “Flee” to your enemies, "Essential"), Seraphim Armour, Personal Void Shield