https://underrail.info/build/?HgMEBgMEEAoAAG0AAAAAeDdLAAA6UAYjQMKgAMKgwqAcAC05KD89KmQuwr0hVynCh8KGBXLCt8KKK8OZwp3CrsOH4qWyBeKmhgrfvA
So, this one I have a soft spot for, seeing this was my first build. I always like playing toolbox mages in games I am permitted to, this one was no different. Took like a week of restartitis to find something I was happy with... I share this so you don't have to. The main unique thing for Tranq Psi is Temporal Distortion. Anything else, even Cerebral Trauma, Psychosis Psi does better; mostly because Trance is a broken af drug.
First things: I think Psi is weak. At least, Tranquility Psi is. Most gun builds can splash 70 TM 140 MT to get the defining psi spells; so the main thing tranquility PSI has going for it is Locus of Control at 10 WIL; and the best silent assassination in game with Temporal Distortion + CC (Mental Breakdown/Cryostasis). Arena single fights are a joke for Tranquility Psi, but outside you'll be spending a lot of time to pull mobs into a single group with Noise/Traps to Thermo Destabilization + Grenade them; because those are your best AOEs, and their cooldowns are large; you don't really have DPS because Psi Points mechanic.
Stealth grenades are the cheat code for Psi, though. Tranq Psi needs almost no charons to do its thing; Psi Inhalants every 2-3 fights is still a lot cheaper than ammo, no repairs involved; and their crafting is pretty cheap. This gives Psi the deepest pockets to spend on consumables, like Stealth nades; the most OP thing for a class limited by Psi Points and Cooldowns.
Default Configuration (Okay against most standard groups of enemies for the majority of the game)
Cryokinesis, Pyrokinesis, Pyrokinetic Stream, Temporal Distortion, Thermodynamic Destabilization, Mental Breakdown, Psycho-Temporal Contraction. Extra Slot(s) go to Stasis, Neural Overload, Pseudo-Spatial Projection; as needed.
Early game, replace Breakdown with Cryostasis.
Late game, Neural Overload is very good against heavy armors, and you can Thermo Destabilize > Neural Overload and kill the target; then Premeditate + Locus + Breakdown the group and finish them off one by one. Can use a TC Muffled NO Filter Headband too.
Default Psi Headband:
Uni-Psi Muffled ExtensionCan replace Psi-Circuit Extension with a Filter (Pyrokinetic Stream/Pyrokinesis typically).
Food:
Psi-Beetle Soup+20% (3 School penalty) -15% (Food) -10% (Vest) -25% (160 Muffler) -10% (PN Flexibility) = -40%. Add Advanced Psi Empathy and use Single School Headband for truly insane reductions.
Enter fight stealthed, unstealth and sprint if needed, Flashbang or Locus Breakdown group; start stacking Temporal Distortions on the toughest guy in grenade radius of everybody. On the 2nd turn (when your Temporal Distortions are about to pop End of Turn), Thermo Destablize before or after finishing stacking Distortions. You want to ensure that guy doesn't die to Distortions, but instead comes as close to 1 HP as you can. Turn 3, main guy is destabilized and close to death, other guys woke up from CC (Flashbang lasts 2 turns); you Grenade/Pyrokinesis or Cryokinesis the Destabilized guy. If Cryokinesis kills him, Destabilization buff doesn't disappear and pops normally; dealing massive AOE damage. Mop up the rest with Cryokinesis/Pyrokinetic Stream as needed. PTC/Adrenaline + Booster/Muffler/Beetle Soup needed for big foes that need a lot of distortions.
So when does this fail?
(A) Other groups get aggroed when you CC the first. When this happens, you either need to pull them first with noise (TNT), bunch/stall with Bear Traps, or just CC them again (Flashbang first group, wait for second group, then Locus Breakdown them all). Or Locus Enrage instead of Breakdown and gamble. Enrage is honestly weaker than I thought; I ended up using it very rarely; since Tranq Psi is so dependant on enemies remaining bunched up for ~2 turns.
(B) All enemies are similar HP, so Thermo Destabilize doesn't kill. If this is because enemies are too weak; use normal AOEs like Pyrokinesis + Grenades; then Locus Breakdown/Flashbang. Then pick them off one by one with Cryokinesis/Pyrokinetic Stream. If they're too strong; you need stealth nades to pop on turn 3 of the combo (when the Distortions pop) to retreat. Consider re-innervating to include Cryokinetic Orb if needed; but remember Orb turns off Destabilization; even if it kills unlike Cryokinesis.
(C) Enemies have high Mech/Heat DR. This is the thing that completely counters your primary AOE source, Destabilization. Groups of robots do this; unfortunately, you don't really have a solution for this; and the main reason why I think Tranq Psi is weak. That doesn't mean you don't though. Continuum Ripple in the build is specifically for this scenario, as is Cerebral Trauma NO and Locus Enrage vs organics. If you have Plasma Beam; it can still be pretty strong in a Tranquility build with massive Psi cost reduction; so you can use it in this scenario. Investing in traps, as always, gives you the I-win button of trap spamming in those scenarios. Traps is also helpful to boost your low trap detection. You do have low carry capacity; keep that in mind. Can be worth taking Pack Rathound instead of Continuum Ripple if you do go for traps.
(D) CRAWLERS. While you can cast Pseudo-Spatial Projection if you have the time; unfortunately the F9 key is your most reliable option vs these. Another reason why I don't think this is a strong build, because crawlers single-handedly make this build Ironman unviable. Take Paranoia, use Detection Goggles, enter Crawler areas with Stealth Armor (not beetle vest) and Cloaking Device active; then Bear Trap yourself into a choke and make sound. Once the first crawler is detected, use flares liberally to reveal the rest. Killing them shouldn't be a problem afterwards. These fuckers are the main reason to go 4 PER instead of 3. Huge quality of life, trust me. Going for DEX 4 is to make it less point intensive to hit ~100 Throwing. You need that since you rely a lot on short range flashbangs.
So, Psychokinesis? Honestly, you can do perfectly fine without it. While Imprint and Grounding sound nice, you don't have slots and usually have better options. The main reason for PK would be 100 for Implosion. With ~100 quality Beetle Vest and ~140 Uni-Psi Headband; you get 275 PK for 75% Max HP Implosion. Recur it with Entropic Recurrance, and everything will die. The problem is, even on Dominating 400% HP; Temporal Distortion is more than enough to oneshot.
Vs these bosses; crafting a Temporal Manipulation Muffled Temporal Distortion Filter headband will do good as well, you don't need Implosion. Tranquility never lacks single-target damage; what it lacks is AOE, and Electrokinesis is nowhere near enough to justify taking PK. Never really played around with Force Field; if it is good I can see PK being good; but even then, slots are an issue.
Take the bare minimum mechanics, biology and tailoring you need to craft the lowest quality beetle vest from the lowest quality carapace using the Underpie in the SGS kitchen as soon as you can. Increased costs is crippling for you, so use that vest to counteract the initial +10% from TM + MT innervation. The next +10% from adding Mental Breakdown comes quite late at ~Level 14 when you take Locus, you already took Psycho-Neural Flexibility at 12 to counteract this. Craft the best uni-psi muffled extension Headband by ~16, secondary module Energy Shields by ~18 (High/Medium or Medium/High is universal enough; keep a Low/Low for Burrowers). Skillpoints will be tight because Neurology needs 35 Bio; but getting your Neurology 25% Muffled Headband is a massive powerspike, as is that Power Management energy shield for explosions.
Join JKK and get the Jacket, and you can go to Expedition with your Persuasion very early; the 2nd raid gives you Spear-Staff, overall best weapon for you (sometimes the others are better). And Philosophy. Seriously, this is one build that wants that 80 Persuation ASAP for just that +15+10 Max Psi. JKK should give better headbands than even Oculus (164 vs 159), but very rarely I assume.
One optimization you can do lategame is Fight Response over Mantra. Adjust your HP with Sturdy Vests so that a Super Hypo heals you ~80% of max HP. Then lower HP to ~20-25% and enter a fight. You gain +10 AP from Fight Response (below 25% HP); then use Doctor's Belt + Hypo (2 AP) to heal to full and re-enable Tranquility. This nets you +8 AP first turn of the fight, but you can't use Hypos for that fight. Doctor feat helps here, letting you use even the highest quality Sturdy Vest with this tactic (as long as you're also equipped with Spear Staff). Whether this is worth it I don't know, I just went with Mantra since the game was almost over already.
Good luck, young padawan. May the force be with you!