UnderRail is a single-character, turn-based CRPG, and psionics — psi — is the optional power system that, for a lot of players, ends up being the easiest strong way to play it. The reason is simple and worth stating up front: a psychic's entire toolbox of abilities is always available. There is no ammo to track, no reload, no weapon to swap. Every encounter becomes an ability rotation — read the room, pick the right tool, spend your psi points, repeat. That clarity is exactly what makes psi forgiving to learn even though, as you will see, the build asks you to play carefully.
This guide is a deep-dive into how psi actually works: how you unlock it and what it costs you, which stats drive it, the four schools, the psi-point economy, innervation, and how to survive as a deliberately fragile character. If you are still deciding what to play at all, the UnderRail build guide compares psi against the gun, crossbow, and melee archetypes.
Which two psi schools to take — ranked
If you read one section, read this one. The multi-discipline tax explained further down means your school choice is the single most expensive decision in a psi build, and skill points spent on a school you abandon are gone. Here is the honest ranking, and why each sits where it does.
| Rank | Pairing | Why it ranks here | The catch |
|---|---|---|---|
| 1 | Metathermics + Thought Control | Metathermics carries your damage from Cryokinesis in the opening hours to Plasma Beam late. Thought Control is the one school that **bypasses armor**, which is exactly what walls conventional damage in UnderRail. Damage plus an answer to armor is the most complete two-school kit. | Both schools want skill points early, so your non-psi skills stay thin for a long stretch. |
| 2 | Metathermics + Temporal Manipulation | Same Metathermics damage core, with Temporal Manipulation buying you turns and layering delayed damage. Excellent action economy once it comes online. | Temporal Manipulation is **Expedition DLC only**. Without the DLC this pairing does not exist. |
| 3 | Psychokinesis + Thought Control | Telekinetic Punch and Force Field are genuinely useful utility, and Thought Control still answers armor. A fine pairing that plays more like a controller than a nuker. | Psychokinesis is the weakest of the two damage schools in practice — you will notice the damage shortfall on heavies. |
| 4 | Metathermics + Psychokinesis | Two damage schools means you delete soft targets fast. | **No control school.** With Psi Empathy stripping 20 to 45 percent of your health, a psychic with nothing to lock a pack down is the build most likely to die in one bad turn. |
| 5 | All four schools | Nothing — this is the trap. | Every extra discipline adds 10 percent to base psi cost, and the innervation cap means you are still choosing 8 abilities. You pay more per cast for a toolkit you cannot fully field. |
Anchor on Metathermics. If you want one rule rather than a table: take Metathermics, pair it with Thought Control, and ignore the other two until you have finished a playthrough. Cryokinesis is free at skill 0 and stays relevant for a surprisingly long time, and Plasma Beam is the late-game payoff. Everything after this section explains the machinery behind that recommendation — what psi costs you, how the point economy works, and every ability in each school with its skill requirement.
What psi is, and why it is beginner-strong
A non-psi character lives and dies by a weapon skill, ammunition, and positioning. A psychic instead carries a set of innervated abilities that are always ready. Because the whole kit is on tap at any moment, you are rarely caught without an answer: a damage spell for a soft target, crowd control for a pack, a debuff for a heavy. Fights stop feeling like improvisation and start feeling like a rotation you can plan.
That is the upside. The honest counterweight is that psi is not free power — it is power you pay for in maximum health, in psi points, and in the discipline to focus. The rest of this guide is mostly about those costs, because understanding them is the difference between a psychic that steamrolls and one that runs dry mid-fight and dies.
The gateway — Psi Empathy and its permanent HP cost
Psi is not on by default. You unlock it by taking the Psi Empathy feat, which in the world means getting a pill from Dr. Pasquale at South Gate Station Medical to disable your psionic inhibitor. From that point you can learn and use psi abilities.
The catch is permanent and you should weigh it before committing the build: Psi Empathy imposes a lasting -20% maximum health. Later, the veteran feat Advanced Psi Empathy raises the total HP penalty to -45%. That is close to half your health bar gone, by design. A pure psychic is one of the more fragile characters in the game, and that fragility shapes every other decision you make.
The HP penalty from Psi Empathy is permanent and cannot be undone. -20% maximum health at first, rising to a total of -45% if you later take Advanced Psi Empathy. Go in expecting to be fragile and to win fights through control and positioning, not by trading blows.
Will and Intelligence — the two stats that drive psi
Two attributes carry a psi build, and they do different jobs.
- Will is your psi potency and a core driver of psi regeneration. It is the headline psychic stat — higher Will means your abilities hit harder and your active pool refills faster.
- Intelligence also feeds psi regeneration, and it does something Will does not: it caps how many abilities you can have innervated (prepared) at once. More on that limit below, but the short version is that Intelligence buys you breadth of toolkit.
You will not max both alongside everything else, so most psi builds prioritise Will for raw effect and invest enough Intelligence to comfortably innervate the abilities they actually want to use.
The four schools
Psi is divided into four schools, each with a distinct role. The first three are in the base game; Temporal Manipulation arrives with the Expedition DLC.
| School | Role | Notes |
|---|---|---|
| Thought Control | Mind effects and control | Fear, rage, and brain overload; notably bypasses armor |
| Psychokinesis | Telekinetic and electrical offense | Telekinetic force plus electricity damage |
| Metathermics | Heat and cold offense | Burning and freezing damage, strong area control |
| Temporal Manipulation | Support (Expedition DLC) | Delayed damage plus buffs and debuffs |
A useful way to read this table: Metathermics and Psychokinesis are your primary damage schools, Thought Control is your crowd-control and armor-ignoring school, and Temporal Manipulation is a support layer that buffs you and debuffs enemies rather than carrying a fight on its own. Most strong psychics pair one damage school with one control or support school.
How you learn psi abilities
Knowing the schools is not the same as owning abilities, and this step trips people up because nothing hands them to you.
There are two routes:
- Trainers. Each of the four disciplines has a trainer at South Gate Station who teaches that school's abilities directly. This is the reliable path and where most of your early kit comes from.
- Psionic Mentors. These devices imprint an ability cerebrally rather than teaching it. Various vendors across the world stock specific mentors, so an ability a trainer will not sell you may still be obtainable as a mentor elsewhere.
Every ability also has a skill requirement in its own school. You cannot buy your way past it - the number below is the school skill you need before the ability is usable, and it is the real reason a psychic keeps one or two school skills near their cap instead of spreading points thin.
Every psi ability by school
Each school's starter ability is available at skill 0, so a brand-new psychic always has something to cast. The interesting breakpoints sit at 25 to 35, where each school's defining tools unlock.
Thought Control
Mind effects - fear, rage and brain overload. This is the school that bypasses armor.
| Ability | Skill required | What it does |
|---|---|---|
| Neural Overload | 0 | Starter attack that overloads the target's mind |
| Frighten | 30 | Induces fear |
| Bilocation | 35 | Duplication |
| Motor-cognitive Transference | 40 | Mind control |
| Psychosomatic Predation | 45 | Drains the target |
| Mental Breakdown | 45 | Causes a breakdown |
| Psi-cognitive Interruption | 55 | Blocks the target's psi use |
| Enrage | 60 | Forces aggression |
| Pseudo-spatial Projection | 65 | Creates projections |
| Neurovisual Disruption | 70 | Sensory interference |
Psychokinesis
Telekinetic force and electricity, and the school that enhances unarmed attacks.
| Ability | Skill required | What it does |
|---|---|---|
| Telekinetic Punch | 0 | Starter attack |
| Force Field | 25 | Defensive shield |
| Electrokinesis | 30 | Electrical damage |
| Telekinetic Grounding | 30 | Electrical control |
| Force Emission | 35 | Force blast |
| Disruptive Field | 40 | Disruption effect |
| Electrokinetic Imprint | 45 | Electric marking |
| Telekinetic Proxy | 55 | Telekinesis at range |
| Psychokinetic Chain | 60 | Chaining strikes |
| Implosion | 70 | Destructive force |
Metathermics
Heat and cold. The strongest area-control damage school.
| Ability | Skill required | What it does |
|---|---|---|
| Cryokinesis | 0 | Starter freeze attack |
| Pyrokinesis | 25 | Fire attack |
| Cryostasis | 35 | Freezes a target in stasis |
| Pyrokinetic Stream | 35 | Flame stream |
| Cryokinetic Orb | 40 | Freezing projectile |
| Cryogenic Barrier | 45 | Ice defence |
| Thermodynamic Destabilization | 50 | Temperature chaos |
| Cryo-Shield | 55 | Freezing shield |
| Exothermic Aura | 70 | Heat emanation |
| Plasma Beam | 90 | Plasma attack |
Temporal Manipulation (Expedition)
Delayed damage plus buffs and debuffs. This school comes with the expansion rather than the base game.
| Ability | Skill required | What it does |
|---|---|---|
| Temporal Distortion | 0 | Starter ability |
| Psycho-temporal Dilation | 25 | Slows time |
| Limited Temporal Increment | 35 | Accelerates time |
| Entropic Recurrence | 45 | Entropy effect |
| Psycho-temporal Contraction | 55 | Compresses time |
| Temporary Rewind | 60 | Rewinds |
| Precognition | 65 | Sees ahead |
| Stasis | 70 | Temporal freeze |
Read those skill numbers against the skill cap, which is 10 plus 5 per character level. Plasma Beam at 90 Metathermics is therefore a late-game commitment, while the 25-to-35 band is reachable early - which is why a psychic's real power spike is the moment a second school skill clears 30, not the moment they take Psi Empathy.
Psi points, the reserve, and regeneration
Here is the economy that decides whether your rotation holds up over a long fight. Post-Expedition, a psi-user has 100 maximum Psi points in their active pool, plus a separate Psi reserve of roughly five times the active maximum that exists to refill the active pool.
Your active pool regenerates each turn. The regen formula is:
5 + (Will + Int) / 2, rounded down.
So a character with, say, 12 Will and 10 Intelligence regenerates 5 + (22 / 2) = 16 psi per turn. This is exactly why Will and Intelligence matter beyond raw potency — they keep your pool topped up between casts.
The reserve is the part that catches people out. Each time your active pool refills, it draws from the reserve. When the reserve empties, psi stops regenerating entirely until you refill it — and the only way to refill it is with psi inhalant consumables. Carry inhalants. Running the reserve dry in the middle of a long fight, with no inhalants on hand, is one of the most common ways a psi build stalls.
Treat psi inhalants like ammunition — always stock several before a known boss or a long dungeon. Your active pool regenerating each turn can fool you into thinking psi is infinite; it is not, the reserve behind it is finite, and inhalants are the only refill.
Innervation and the focus-one-or-two-schools rule
You cannot simply use every ability you know. You must innervate them first — effectively prepare a loadout of active abilities. The number you can innervate is capped:
2 + Intelligence / 2, up to a maximum of 8 (rounded down).
So Intelligence is what widens your toolbox, but even at the cap you are choosing 8 abilities, not 30. That alone forces selectivity.
The second, more important rule is the cost penalty for spreading across schools. Innervating abilities from multiple disciplines adds +10% base psi cost per extra discipline. Run two schools and there is a modest tax; run all four and every spell costs dramatically more psi. This is a deliberate nerf to "all-school" psi, and it exists to push you to focus one or two schools rather than dabble in everything.
The practical takeaway: pick a damage school and a control or support school, innervate the best abilities from those two, and leave the rest alone. A focused two-school psychic spends far less psi per turn and hits much harder than a four-school generalist who burns out their pool in two casts.
-
1
Choose your core two schools
Pair one damage school (Metathermics or Psychokinesis) with one control or support school (Thought Control or Temporal Manipulation). Resist the urge to add a third.
-
2
Set your Intelligence for the loadout you want
Innervation cap is 2 plus Intelligence over 2, max 8. Invest enough Intelligence to slot the abilities you actually use, and put the rest of your weight into Will.
-
3
Build a clean rotation
Open with crowd control, follow with your damage school, and keep a panic button (a freeze, a fear, or a knockdown) innervated for emergencies.
-
4
Stock psi inhalants
Your reserve is finite. Carry inhalants for long fights so an empty reserve never ends a rotation early.
Playing fragile — positioning and crowd control
Because Psi Empathy strips a large chunk of your maximum health, a pure psychic cannot afford to trade blows. The good news is that psi gives you exactly the tools to avoid trading at all.
Lead with control. Thought Control can lock down a pack with fear or rage and notably bypasses armor, which matters against the heavily armored enemies that shrug off conventional damage. Metathermics can freeze enemies in place while you burn them down. Psychokinesis can knock targets back and create space. Used well, you are deleting or disabling threats before they ever reach you.
Positioning does the rest. Fight in doorways and corridors so you only face one or two enemies at a time. Open from stealth or from range when you can. Keep an escape or a hard crowd-control ability innervated so a bad initiative roll does not end the run. With -20% HP — and -45% if you took Advanced Psi Empathy — a single bad turn in the open is far more dangerous for you than for almost any other build, so the discipline of never getting surrounded is not optional.
For character creation, the opening hours, and where psi fits into early progression, see the UnderRail beginner guide.
Bringing it together
Psi earns its reputation as the easiest strong archetype because the toolbox is always in your hand — but that reputation hides three real costs you have to respect. You pay in permanent health for the Psi Empathy feat, you pay in psi points and a finite reserve that only inhalants refill, and you pay a focus tax that punishes spreading across all four schools. Honor all three — focus one or two schools, manage your pool and reserve, and win through crowd control and positioning rather than durability — and psi becomes one of the most reliable and satisfying ways to play UnderRail.
