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- 1 Psionic Aliens
- 2 Countering psionic attacks and tactics:
- 3 Psionic Soldiers
- 4 Psionic Formulas
- 5 Walk-through for a Psi Attack
- 6 Summary of Alien Psionic Resistance
- 7 Summary of Alien Psionic Attack Strength
- 8 Alien Psionics Targeting
- 9 See Also
Sectoid Leaders, Sectoid Commanders, and all Ethereals, have Psionic abilities to create Panic (reduce Morale) or attempt Mind Control. Be very wary. Murphy's Law says the first soldier to succumb to Mind Control will be in the perfect position to shoot your squad in the back with a Rocket Launcher.
If an alien spots any member of your squad, even the tank, during the alien turn, the squad is at risk of attack. The weak soldiers will be targeted most often, and will likely be nicknamed "psi-puppets" by their teammates, if anyone survives. Any soldiers found to be psi-weak should be just fired outright. Taking them off the combat roster and giving base-defense duty serves little purpose... you are essentially paying monthly salaries for them to do nothing. Base defence is always performed by a full Battleship crew... so if your base comes under attack by Ethereals or Sectoids, any psi-puppets are a liability instead of an asset.
Countering psionic attacks and tactics:
The former doctrine on psionically attacked soldiers also applies to soldiers who have been psionically screened. Namely, soldiers weak in psi-strength or who have become victims of psionic attack should be sacked or re-assigned at the earliest opportunity for the safety of the rest of the squad. If retained on active duty they should never be knowingly sent on missions against psionic capable aliens. Veteran soldiers who are psionically weak but otherwise worth keeping can be assigned to a secondary craft or interception base, strictly for use on missions against Mutons and other non-psionic aliens.
JellyfishGreen: I tried jotting down the names of the puppets as a reminder to fire them later, or use as decoys.
Covenant: Another good way is to go right from the mission's conclusion to the soldier menu and add a symbol or word to their name so it is instantly recognizable who got mind controlled, and who successfully resisted. Handy for picking subjects for psi-training before you know their strength levels.
Some commanders forgo any chance of reaction fire, and have all soldiers drop their weapons at the end of the turn and pick them up on the next turn. Should any soldiers be mind-controlled in the intervening alien turn, at least they'll be unarmed.
Test results tell us the soldier with the highest chance of a succesful psionic attack is always chosen as the victim, even if he's out of line-of-sight of either enemy or ally. (The game AI is skipping any LOS requirement) This usually means the aliens concentrate on the weakest psi defence soldiers, though they will switch targets depending on distance. - Psi-puppet soldiers should NOT be used as alien hunters. Disarm them as soon as possible, preferentially before the mission.
If such soldiers are deployed against psionic capable aliens, they may still have use in limited roles. Do not give them any weapons or grenades. Well, maybe smoke or proximity grenades.
- Unarmed medic, equipment operator, ammo carrier. If controlled, they cannot injure other soldiers. If panicked, they'll drop the equipment, if placed in their hands.
- Non-lethal weaponry. Small Launchers prevent injury of other soldiers but the risk of control and loss of tactical advantage remains.
- Stun Rods are non-functioning weaponry in the hands of the aliens. Any soldiers under alien control WILL NOT ATTACK using them.
- Miner. Arm them with Proximity Grenades. Unlike those pesky aliens, your agents are smart enough not to get blown up by these things, right? (Just pick them up off the ground). Beware that your panicked soldiers seem to be drawn to Proximity Grenades like iron filings to a magnet. Probably due to Murphy's Law.
- Decoy. The unarmed soldier lets themself get mind-controlled rather than shot. If they are under mind control, the soldier will often be spared by the alien. Every mind-control attack on the "decoy" is one less attack on the rest of the squad and one more psionic alien kept busy. Note your other soldiers may shoot a controlled decoy on sight, and the aliens will shoot a panicked decoy on sight. An extremely risky tactic for the soldier but survival can be extended by blockading the decoy into a closet with other soldiers or tanks and turning your back to them. (which is ridiculous since you are taking 2 soldiers out of combat to prevent losing use of 1 soldier during combat)
- Jack of all trades. Soldier is meant to be a decoy, and carries, Stun Rod in hand, and flares, medkit and smoke grenades. Soldier is also considered "expendable" and thus fulfils role as forward scout during scary situations.
- Launcher Operators. Simply a soldier with a launcher and no ammo. The soldier either stands on a pile of ammunition, or is handed the ammunition on demand in combat. Once the weapon is loaded, the round is immediately spent before the end of the turn. This way, if controlled, the soldier will have an empty weapon and thus be harmless. This allows the weak willed soldier to contribute somewhat to the fight whenever you regain control of them.
- Suicide Bomber. Give this troop no equipment. March him towards a heavily guarded alien ambush. Just before walking him into it, have someone else arm a Heavy Explosive, throw it to him and make him pick it up. Have him walk into the trap and get mowed down by hidden alien reaction fire. End turn. BOOM.
If there are two or more psionic aliens, you may need more decoys to keep them all busy.
Stubbs: According to the Mind Control section of this wiki, XCOM operatives do not reaction fire at mind-controlled friendlies. Which is correct?
Kill the puppetmaster.
Find and kill the alien doing the mind control. This will free those who were under its control. The mind controller is frequently the highest-ranking alien you're facing, which means you'll likely need to penetrate the command center of the structure you're facing.
Remember that killing the aliens' ranking officers imposes a major morale penalty to the invaders, another bonus that shouldn't be underestimated. Many commanders have seen a seemingly invincible, mind-controlling attack force reduced to panic in the instant their commander is shot down. Even against Ethereals, all of which have psionic capability, this tactic is useful, since it will often buy you a round or two before other units start using Psionics and can panic even them.
Must... Fight... Harder... DIE!
If you can force a very successful round of attacks, the morale penalty this imposes on the aliens may bring on panic, which would bring a temporary stop to their psionic attacks. Such a round also raises the morale of your own troops, which will temporarily help combat panic attacks.
Roll with it.
Kamikaze tactics have also been used but cannot be recommended here.
HWP's can continue to be used in all roles against psionic capable forces as they are immune.
If all forces are equipped with Power Suit, which is proof against light ballistic weaponry, standard rifles and pistols can be freely issued with little risk of lethality even if counterused. Note Ethereals are less affected by these weapons than Sectoids. For them, we recommend the Auto-Cannon/HE.
- JFG, with credits to the adventurous NKF-sensei whose field reports I freely draw from. --JellyfishGreen 14:50, 19 Apr 2005 (BST)
-MikeTheRed: In my experience, laser pistols can hurt you in flying suits. Specifically, if you're shot in the back. So they are great for "firing squads" (all your guys facing MC'd aliens), but not when aliens might MC you. (And don't turn your back when doing a firing squad!)
-NKF: " Just to add to this, a laser pistol, with 46 laser, does between 0 - 92 damage (See: Damage). Therefore, only your front plates will be truly invulnerable to laser pistol damage. On the other hand, you have a chance of being damaged from pretty much every other direction, and you cannot always guarantee that you'll be facing your attacker at all times.
The only real consolation is that laser pistols won't kill you outright for each hit, but lots of little hits can indeed build up to a lot of damage. I'd much rather recommend an autocannon/HE or the standard pistols/rifles for this exercise. Direct hits from the ACHE can probably cause a tiny amount of damage, but the ammo will not be unlimited like the laser pistol, and the autocannon is also the slowest burst weapon in the game, despite its name, which gives you time to get away and seek cover. Another bonus is that it works a lot better on superhuman ethereals than the pistol/rifle! "
You won't know exactly what your soldiers' psionic strength are until you run them through some form of screening process, running them through a Psi Lab in batches of 10. Soldiers with a high Psionic Strength (80 or higher) should be trained further and kept in the "rear guard" during combat. Do not use them as scouts, or front line troops -- they will soon become your most valuable soldiers.
After a month or two of Psi training, your best soldiers will be able to mind-control weaker aliens, such as Mutons. Your soldiers' Psi Skill can be increased very quickly by equipping them with Psi-Amps, leaving them in the Skyranger, and having them attempt to panic units every chance they get. See Experience Training#Psionic Skill training for more details.
Pre Psi-Lab Screening
An efficient, if brutal, method for screening your troops for psionic ability is to use the first psychic alien you encounter. A supply or terror ship with a Sectoid Leader is recommended.
Kill all the lower ranked aliens, and secure the UFO using usual tactics (a psi-decoy is useful in this regard). If the ship is reasonably intact, the Alien leader will not usually leave the bridge, even after turn 20.
Gather your troops into the UFO, get any soldiers who are targeted to throw their weapons, then stun or kill the most susceptible soldiers until the remaining soldiers are immune to Mind Control, and the Alien frequently fails to panic units (you can check this by keeping track of morale).
- A side benefit of this is bravery training. If the weaker soldiers are killed rather than stunned, those who remain will very quickly reach 60 or 70 bravery. Leaving the highest ranked soldiers at home, or using the bravest soldiers to target the rookies, will help in this regard.
A more precise but much more tedious addition to this tactic is to arrange your troops in a line intersecting the UFO. Any soldiers attacked move away until another soldier is attacked instead. You may still have to stun or kill the weakest soldiers as the map may not be large enough.
- At the end of this process you will have your troops neatly sorted by psi-strength with the distance being proportional to the difference.
- If the line ends directly under the bridge and the closest soldier is never attacked, this will give you a lower bound for the psi-strength of your entire (surviving) force.
Given five large, Sectoid UFOs, this method will, on average, give you a Skyranger full of elite (>80 PST) psi warriors all ready for training when you finally build a psi-lab.
My New Pet Alien
Some skilled psionic operators have had success with simply attempting control of every alien encountered and disarming them, then using the controlled alien as a scout to find more aliens, then controlling the newly discovered alien as a new scout and leaving the old one for a mop-up squad, repeat process as TU's permit.
Easiest actions with a controlled unit are movement and firing or dropping the held weapon. It is possible but tricky to do more (see Alien Inventory Trick.) Disarmed aliens make for excellent Experience Training fodder.
Remember aliens will revert to alien control unless re-aquired on the next turn.
Controlling the Board
Once you start taking control of aliens that are psionic themselves, this has a certain avalanche effect as you can spend the alien's TU's on mind control as well. As noted in Exploits you do have to throw them a spare Psi-Amp to take advantage of this.
The equations governing psionics are as follows:
Attack Strength (AS) = INT( Psi Strength * Psi Skill / 50 ) Attacker stats Defense Strength (DS) = INT( Psi Strength + ( Psi Skill / 5 ) ) Defender stats Attack Success (A%) = 100/56 * ( Constant + AS - DS - Distance ) where Constant = 25 for Mind Control 45 for Panic
Attack Chance (A%) is a number (0 to 100), not an actual percent (0.00 to 1.00). Values less than 0 mean guaranteed failure, and greater than 100 mean guaranteed success.
It's quite significant that Attack Strength is geometric... a soldier with 100 Psi Strength and 100 Psi skill is not 100 or 200 times better than a soldier with 1 Psi Strength and Skill... he is 10,000 times more powerful at Psi attacks.
These formulas differ slightly from the ones that appear in the Official Strategy Guide, but have been discovered through testing and are believed to be correct.
The further away a target is from its attacker, the lower the chance an attack will succeed. Distance follows the "walking TUs" method, where a distance 10 tiles directly lateral equals 10 in the equation, but diagonal distances are more. For example, 10 tiles away on a pure diagonal is considered to be 15 tiles away; see this for more on Walking TUs distance. The distance factor means that beyond a certain point, aliens can only panic certain units, not mind-control them.
Overall, it's clear that Psionic Strength plays the greatest factor in defense, and that Panic Attacks are more likely to succeed. (a flat 36% higher chance than MC) But Mind Control is much more... useful. Overall, it is probably best to attempt panic attacks when the chances of MC are below 5% ... it can be argued that 8 successful panic attacks are better than 1 successful MC... unless of course you are targetting an alien carrying Blaster Bombs. Once MC chance is 18% or higher, MC is better, since the ratio becomes 3 panics to 1 MC. Anything in between is probably the commander's preference.
For an in-depth exploration of the psionic equations, including minimally and maximally effective soldier psi values versus the various aliens in the game, see Psionic Equations.
Walk-through for a Psi Attack
A number of factors affect the results you might see, especially for panic attacks. Here's a walk-through to make everything clear.
For the Psi Attack itself, only these factors matter:
- The Psi Attack Strength of the attacker; both Psi Strength and Psi Skill matter here (see equation)
- The Psi Defense Strength of the target; mainly Psi Strength matters here, but high Psi Skill helps a little
- The distance to target
Nothing else matters - the target's current Morale or Bravery, etc., do not affect the chance of a successful psi attack. The Psionic Formula alone determines the chance. It is described briefly above, and in much greater depth here.
If the attack is successful, the soldier gets 3 Experience points added to the counter that determines how much Psi Skill might improve when the mission ends. If the attack fails, they only get 1 point added to the counter. This is the only result of failed attempts; the target is not affected in any way by a failed attempt (but the attacker just ate some TUs, of course).
Past the fact that different soldiers are likely to have different attack skills and distances to a target, it does not matter if one soldier performs a number of attacks, or many soldiers perform one attack. Each attack is simply one attack, and each attack gives experience even if the target is already panicked to 0 Morale.
If you performed a successful mind control attack, the target is immediately MCed - and you can stop reading the walk-through here. But if you want to understand more about successful panic attacks, continue reading.
- All soldiers and aliens start battle with a Morale of 100.
- Recruits have Bravery from 10 to 60. The maximum possible value is 100.
- Thus, a successful panic attack can cause a soldier to lose from 10 to 100 Morale: 10 if they were a superman at 100 Bravery, and 100 if they were a wimp with 10 Bravery.
- All non-terrorist aliens have a Bravery of 80 regardless of game difficulty level, which means they lose 30 Morale with each successful attack. Terrorists have values as follows:
- 90: Celatid, Reaper
- 100: Cryssalid, Silacoid
- 110: Cyberdisc, Sectopod (although you can "successfully" panic attack an alien robot, as shown by the experience counter, it can't actually affect them!)
- While 30 Morale may not seem like a lot (and 80 Bravery may seem high), remember that the chance of a successful attack is based mainly on the target's Psionic Strength; Bravery is not involved at all. And, as the psionic formula shows, it is MUCH easier to panic a target than to MC it... panic has a +35.7% higher chance, due to the difference in the formula's constants.
- The amount subtracted from Morale is not subject to chance or variability, for a given target. It is always exactly 110 - Bravery. The variability comes from whether the attack was successful (above), and whether the demoralized target misses its panic roll (below).
- Panic attacks do not give any success or failure message. Here are some ways to see their Morale:
- Use a Mind Probe. It is not psi dependent, so psi-locked soldiers (not trained in the Psi Lab yet) can check the success of soldiers with low Psi Skill (and thus a low chance of inducing panic) when you first get Psi capability. But remember, the Mind Probe does not give psi experience.
- You can MC the alien and look at his stats. But this would freeze him for the current turn, and, of course, if you are able to MC, many won't bother with panic.
- If really determined, you can look at UNITREF.DAT offset  for the alien. Mainly only hackers or testers would do this, though.
- Also, working through the Psionic Formula for a few cases can give you a feel for how likely success is - i.e., how likely it is that you caused the alien to lose 30 Morale points. Even in the best case, though, a target must be attacked at least twice to have any chance at all of panicking, and at least 4 times to have a possibility of being at 0 Morale.
- If a unit panics or berserks, it always regains 15 Morale when done.
- Also bear in mind that a number of other events can also cause units to lose, or even gain, morale.
- For the record, units go berserk about a third of the time that they panic/berserk.
- Anyone interested in more details on the chance of being successfully psi attacked by aliens should see Psionic_Equations#Aliens_Vs._X-COM.
Summary of Alien Psionic Resistance
Figures are for (any rank)/Leader/Commander, Beginner level - Superhuman level
Fractional portion (if any) is rounded off.
Grouped according to species, in order of increasing psi defence:
Muton: 25 - 29 Celatid: 60 - 69 Silacoid: 80 - 92
Reaper: 35 - 40 Floater: 35/40/45 - 40/46/52
Snakeman: 40/45/50 - 46/52/58 Chryssalid: 50 - 58 Zombie: 80 (all Zombies have Beginner-level stats)
Sectoid: 40/60/62 - 46/70/72 Cyberdisc: 100 - 116
Ethereal: 58/69/75 - 67/79/89 Sectopod: 100 - 116
A soldier with 80 Psi Strength & Skill can Mind Control even a Superhuman Sectopod 20 squares distant about 30% of the time; a soldier with 90 Str and 100 Skill will succeed 100% of the time at that distance. Each unit of distance between the target and attacker will increase the difficulty by almost 1.8% (or, if nearer, decrease it).
Summary of Alien Psionic Attack Strength
Figures are for Beginner level - Superhuman level
Fractional portion (if any) is rounded off.
Sectoid Leader: 50 - 67 Sectoid Commander: 60 - 80 Ethereal Soldier: 40 - 53 Ethereal Leader: 54 - 71 Ethereal Commander: 65 - 87
Given the formulas above, this means your soldiers need a psionic Defense Strength of 131 to be completely immune to a psi panic attack from a Superhuman Ethereal Commander, and a Defense of 111 to be immune to Mind Control attacks. A Defense Strength of 131 can only be achieved with very high Psi Strength and Skill (100 PStr + 155 PSk; 90 PStr + 205 PSk; etc.). However, aliens are typically going to be 10 or more squares distant from your troops, and if you give your troops extensive Bravery training, panic attacks become far less effective. Therefore, a Defense Strength of 100 plus Bravery at 80+ is generally sufficient to shrug off nearly all psionic attacks; this can be achieved by soldiers with a Psi Strength of 80 + Skill of 100, or even soldiers with 95-100 Psi Strength and little to no psi training.
The best defense is a good offense, however; by the time you have such high-level Psi troops, you will probably be able to mind-control nearly any unit on the map long before they can even spot you (see Exponential Mind Control).
Alien Psionics Targeting
If any of your squad members, even a HWP, is visible to any alien during the Alien Turn, every member of your squad is at risk of attack from any psionic aliens, regardless of whether the spotter is psionic. It should be noted that once you pass Turn 20, all of your squad members and their locations are revealed to the AI. This means you can expect a steady stream of psionic attacks after that turn. Your soldiers are also revealed to the AI if there are only two or (or fewer) units under permanent Alien control.