Psionic abilities can be seen as Underrail's equivalent of magic, game mechanics-wise. They're combat abilities that require psi points to use.
Due to a recent genetic mutation, humans in Underrail have varying levels of psionic potential. No one is really sure how this genetic trait came to be, but research indicates that it is a relatively recent genetic mutation. However - it seems to be artificially designed mutation, since so many things about the mutation are just too complex and convenient to be random ones. Hal Roche argued the countrary, believing the mutation would've been way too complex to engineer with existing technology.
The player character also has this psionic potential, but it must be unlocked early on in the game by taking a pill that disables your brain's psionic inhibitor, thus granting you Psi Empathy. There is also the option of not taking the pill at all, leaving your character healthier but without any psionic capabilities.
All characters with Psi Empathy have 100 max psi points, but also a permanent 25% penalty to max health. Psi pool does not scale with any character statistics, but it can be slightly increased with certain psi feats. Psi regenerates every turn in combat and every 5 seconds out of combat. The regeneration scales with Will and Intelligence:
psi regen = 5 + (will+int)/2, rounded down.
The power of psi abilities is determined by the invoker's effective psionic skill, which in turn is determined by skill points put in the skill modified by Will score and synergies from other psi skills. Most damage-dealing psi abilities deal increased damage with higher skill, but psi abilities may also scale in other aspects, such as Pseudo-spatial Projection which projects an additional copy for every 40 skill points in Thought Control. Some psi abilities such as Cryostasis do not scale at all with the invoker's skill.
Unlike most other attacks, offensive psionic abilities cannot miss their targets unless otherwise specified. Most targeted psionic abilities can be invoked through chainlink fences and gates, excluding physical projectile attacks which cannot pass through them (Cryokinesis, Cryokinetic Orb and Pyrokinesis.)
Alpha versions prior to 0.1.14.0 had no psi regeneration. Instead, will score and level determined max psi points. The changes were made to make psi cost more relevant when choosing what to invoke. Abilities that were meant to be used as primary attacks have a low cost and can be spammed without running out of psi. However, high impact abilities can run you out of psi quickly.. In the early implementation of psi regeneration, between versions alpha 0.1.14.0 and beta 0.2.0.0, the regeneration did not scale with any character statistics.
Thought control discipline consists of manipulating the minds of living targets, such as overloading their brains, making them flee in fear or attack everything in blind rage. Damaging mind control abilities directly affect the mind and cannot be resisted with armor. Thought Control skill also rarely opens up new dialog choices, particularly against other mind controllers.
The Psychokinesis discipline is similar to telekinesis with additional electric powers. It can also be used to enhance unarmed attacks. Offensive psychokinetic abilities deal Mechanical or Electricity damage and may also stun targets.
Metathermics, also known as thermal control is the area of psionic development that deals with instigating rapid temperature changes and chemical reactions. Offensive metathermic abilities deal Heat or Cold damage.
Temporal manipulation psionics manipulate time on a very local level to the invoker's favor, primarily featuring delayed damage and buffing/debuffing. It functions well as a support skill that can be incorporated into other character builds, rather than a primary skill around which a build is made.
There are two primary ways of learning new psionic abilities: either have a skilled psionic teach you, or use cebebral imprinting technology in the form of a Psionic Mentor device.
There is a trainer of each psionic discipline in South Gate Station.
- Ezra is the thought control trainer. He can be found on the SGS level 7 cyber labs.
- Bisson is the psychokinesis trainer. He can be found on the SGS station platform or at the gym on the medical level.
- Quinton is the metathermics trainer. He can be found on the SGS agronomy level.
Several traders have psionic mentors for sale.
- Anastasia from Fort Apogee has Telekinetic Proxy.
- Doc from Rail Crossing has Enrage.
- Estelle from Foundry has Thermodynamic Destabilization.
- Ezra from SGS has Neurovisual Disruption (late in the game).
- Heidi from Core City has Telekinetic Proxy.
- Investigator Kiro from Institute of Tchort has Psi-cognitive Interruption.
- Lost Vault Trader has random Psionic Mentor
- Phyllis from Oculus has Pseudo-spatial Projection.