What is the best tech-priest build in Mechanicus?

A Cognition priest first — Lexmechanic abilities for CP generation, Lexmechanic arms for the only +20% dodge in the game and Dominus legs for +3 HP and +3 movement. CP is what pays for extra moves, summons and every weapon beyond the starting pistol, so this priest is what makes your other priests work. Build it before you build damage.

How much energy armour can I actually stack?

Four from armour pieces: Tech-Auxilium head gives +2, a Dominus or Enginseer torso gives +1, and Enginseer legs give +1. That fully mitigates any energy hit of 4 or less. Physical armour tops out at +2 over the same four slots, because only heads and torsos carry it — which makes energy defence twice the investment opportunity physical defence is.

How many augment slots do I get?

One per level-up, capped at level 25. Armour costs one slot each, while equipment and weapons cost one to three. So a finished priest is allocating 25 points across four armour pieces plus whatever weapons and equipment the build needs, and the weapons are where the budget actually goes.

Is it better to buy a full discipline set?

Almost never. The strong pieces are spread across trees — the only +2 energy armour head is Tech-Auxilium, the best legs are Dominus, the only dodge is Lexmechanic — and each tree also contains padding you would be paying a level-up for. Mix deliberately, accepting that each outside tree costs an extra level-up for its prerequisite ability.

Should my priests be tanky?

Less than you would think. A dead priest returns next mission and costs 10 Blackstone per point of maximum HP, so stacking health makes your casualties more expensive rather than less frequent. Dodge, energy armour and simply not being in range are cheaper forms of survival than a larger health bar.

Can I fix a badly built priest?

No. Level-up spending cannot be reset, and each level costs progressively more Blackstone. This is the single strongest argument for deciding a priest's role before spending anything on them, and for keeping one priest deliberately generic early while you learn what the campaign is asking for.

Mechanicus Best Builds — Three Tech-Priests Ranked

A tech-priest is a budget. You get one augment slot per level-up, capacity stops growing at level 25, armour costs one slot each while equipment and weapons cost one to three, and none of it can be reset. Level-ups also get more expensive in Blackstone as you go, so the priest you build at level 8 is largely the priest you finish with.

That makes these worth planning. Below are three complete priests, ranked by what they do for the squad rather than by their own stat lines.

The three builds — ranked

Rank	Build	Armour pieces	Why it ranks here	The catch
1	Cognition engine	Lexmechanic arms (+2 HP, +20% dodge), Dominus legs (+3 HP, +3 move), Lexmechanic head (+1 physical, +1 energy), any +4 HP torso	CP is what pays for extra movement, summoning Skitarii and firing anything above the starting pistol. This priest produces the resource every other priest spends, so it is worth more than its own damage suggests. The +20% dodge on Lexmechanic arms is the only dodge in the game and it is on exactly the priest you want to keep alive.	It contributes little directly. If you measure priests by their own kill count this one looks like a passenger, right up until you try a mission without it.
2	Dominus range specialist	Dominus head (+2 HP, +1 energy), Dominus torso (+3 HP, +1 energy), Dominus arms (+1 energy damage), Dominus legs (+3 HP, +3 move)	The only build where a full set is correct, because Dominus is good in all four slots. The discipline's flat +4 range on ranged weapons applies every turn with no condition — no positioning requirement, no cooldown, no setup. +3 movement on top means it reaches firing position on turn one.	It spends Cognition rather than making it, so it is only as good as your CP economy. Built first, it idles.
3	Energy wall	Tech-Auxilium head (+2 energy), Dominus or Enginseer torso (+1 energy), Enginseer legs (+1 energy), arms free	Four energy armour fully mitigates any energy hit of 4 or less, which removes a whole category of chip damage from the mission. The arms slot is left open deliberately — take Lexmechanic for dodge or Secutor for +20% crit depending on what the priest is for.	Four trees for four pieces is the most expensive shopping list here, because each outside piece also needs that tree's previous ability. Budget roughly eight level-ups for the armour alone.

If you build one thing first, build the Cognition engine. Everything else in Mechanicus is downstream of having CP to spend, and a damage priest built before the economy exists spends its early missions firing a pistol. Everything below is the arithmetic behind these three.

The asymmetry nobody mentions

Armour pieces carry energy armour and physical armour, and they do not carry them equally.

Slot	Best energy armour	Best physical armour
Head	Tech-Auxilium +2	Explorator / Lexmechanic / Enginseer / Xenarite +1
Torso	Dominus / Enginseer +1	Explorator / Tech-Auxilium +1
Arms	none	none
Legs	Enginseer +1	none
Maximum	+4	+2

So a priest can be built to shrug off energy hits of 4 or less entirely, and cannot be built to do the same against physical. Energy defence is twice the investment opportunity physical defence is, and physical damage is better answered by dodge (Lexmechanic arms, +20%) or by not standing there.

Best-in-slot, by what you want

Want	Head	Torso	Arms	Legs
Maximum HP	Explorator / Secutor / Dominus / Xenarite (+2)	Xenarite +5, else Tech-Auxilium / Secutor / Lexmechanic (+4)	Xenarite +3, else Secutor / Lexmechanic / Enginseer (+2)	Dominus / Secutor (+3)
Energy armour	Tech-Auxilium +2	Dominus / Enginseer (+1)	—	Enginseer (+1)
Physical armour	Explorator / Lexmechanic / Enginseer / Xenarite (+1)	Explorator / Tech-Auxilium (+1)	—	—
Damage	—	—	Explorator (+1 physical), Dominus (+1 energy)	—
Crit or dodge	—	—	Secutor / Tech-Auxilium (+20% crit), Lexmechanic (+20% dodge)	Xenarite (+20% crit, +2 move)
Movement	—	—	—	Dominus / Explorator (+3)

Do not build for hit points by default. A priest who falls in battle returns next mission and you are fined 10 Blackstone for every point of maximum HP they had. Stacking health does not reduce how often you lose a priest — it raises what each loss costs. The tankiest priest on the field is also the most expensive one to drop.

Spending the 25 slots

1

Weapons and equipment first, in planning terms

Armour is one slot each, but equipment and weapons run one to three. Four armour pieces is four slots out of 25 — the other twenty-one are decided by what your priest is holding, so plan the weapon before the outfit.
2

One tree deep, then pieces

Take enough of your main discipline to reach the abilities you want, then buy outside armour pieces individually. Each outside piece is two level-ups (the prerequisite ability plus the piece), so three outside trees is six level-ups of overhead.
3

Keep one priest generic early

No respec means an early specialisation made on bad information is permanent. Leaving one priest broadly built for the first few missions costs very little and buys you information about what the campaign actually asks for.
4

Check the level 25 cap before committing to a heavy weapon

Capacity stops growing there. A three-slot weapon plus a three-slot piece of equipment is a quarter of the total budget, and you cannot free it up later.

Mistakes that cost the most

Building damage before Cognition. The damage priest cannot fire its expensive weapon without CP.
Buying complete sets. The strong pieces are scattered and the sets contain padding you pay a level-up for.
Stacking HP on a frontliner. It raises the fine when they fall rather than lowering the chance.
Reaching for a fourth tree. Two level-ups of overhead per outside tree adds up faster than the pieces are worth.
Improvising. There is no reset, and levels get more expensive as you go.

For the campaign clock that decides how much Blackstone you will ever have, see the awakening guide. For where the level-ups go, see the discipline tier list. New players should start with the beginner guide, and the honest review covers the itemisation problem underneath all of this.