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Xcom Exploits Readme

This page lists the exploits currently found within Xcom:Enemy Unknown and Xcom:Terror From The Deep.

The following categories primarily concern the first game in the series, Enemy Unknown, but can also be used with Terror From The Deep, unless noted.

Disclaimer: to do







To Do List

For writing up

  • Destroying unique alien type/rank combos by way of transfering to a throw-away base with a containment + lab (nothing else necessary), starting research on the uniques, dismantling base completely. Repeat ad infinitum. Not exactly a very exciting exploit, but a useful one to know.

For Free

Phantom Radar Trick

The radar coverage of your base is calculated only when a module is constructed at your base. Therefore, once you have a radar built, you can dismantle it, and your base will continue to retain the detection abilities of that radar until you order another base module of any type to be built. This allows you to make your base slightly smaller than it would be otherwise. However, the practicality of this bug is small, because the maximum maintenance for a radar is 35K per month for the Hyper-Wave Decoder, and dismantling the radar will trigger the Paying For Dirt bug. And if you attempt to rebuild over the square to avoid said bug, you will lose the Phantom Radar. So this exploit is only useful if you have spare cash and need a slightly smaller base. More data in in NKF:Talk

Infinite Fuel

This trick is great for saving Elerium-115. When you finish building a new ship, load it out with weapons (dual Plasma Cannons are recommended) and wait for it to have the "Ready" status. Then, transfer it to another base. Immediately after it arrives, tell it to go to a random point on the globe (preferably where you have no bases) and have it patrol in the area. Clicking on it will show that its fuel tank is 0% full. This ship will now have unlimited fuel until it returns to base. This works best on Firestorms, as they have the same number of guns as the Avengers yet cost less.
Note: After downing a UFO, this ship will automatically head back to base. Be sure to send it on patrol again before reaching base, or you will lose the unlimited fuel feature. Because of this, it helps to keep it patrolling as far away from its base as possible.

Free Manufacturing

In the Workshop screen, choose an item to be manufactored, but assign no engineers to it. Also, make sure it's set to produce 0 of the item. Click OK, then go back and assign as many engineers as you want (preferably as many as possible). This time, change the quantity to 1. When the production is finished, you will have gotten one of the selected items--for free! Doing this with tanks and then selling them works wonders on your finances. Playing with the numbers shows that the Hovertank/Plasma is best for this, when considering only Sell Price ($980k) divided by Engineer Hours (1,200), leading to the best "profit" of $817 per engineer hour. Earlier in the game, the Laser Cannon is best at $703 per Engineer hour, but takes only 300 engineer hours. The Tank/Laser Cannon only returns $495 per engineer hour, but takes 1,200 hours, so you won't have to start manufacturing as often.
Note: Although it may be tempting to create fleets of free Avengers like this, you must still have adequate hangers, severely limiting your options. Still very useful, though!
NKF Quick notes:

  • It doesn't matter if you assign engineers to a 0 item build project, because the engineers will be taken off the project anyway.
  • In a similar but completely opposite vein, if you start a project with a certain number of items to build, the required cash for the first item (and perhaps materials) will instantly be taken from you. And if you cancel the project before the job is done, you will not be refunded. It's mainly a loss if you're low on resources, otherwise most players won't even notice the fact that the resources for the first item were never refunded. This doesn't happen if you start a 0 item build project, and then assign staff and a build amount later. This in effect makes the first item in the build list free.

Free Wages

At the end of the month, all your soldiers, scientists and engineers collect their pay checks. Unless, of course, they are in transit between bases, in which case they are unable to reach the guy holding their paychecks before he closes up shop. That is to say, the game forgets to add them to your monthly expenses. The trick here is to have labs and workshops in two bases, and just before each month ends, relocate your staff. They can start working as soon as they arrive, and you don't have to pay them - saving you anywhere up to several million dollars each month.This trick does not appear to work with leased aircraft (Interceptor, SkyRanger). Whilst being transferred, the costs of these aircraft disappear from the Base Information - Monthly Costs screens. However, if the end of month occurs while the aircraft are being transferred, the lease costs are still deducted from the XCom funds.

Extra Ammo Collection

Any partly-used clips will be discarded at the end of combat. However, in DOS versions of X-COM, partly-used clips (in X-COM or alien weapons) will be kept as full clips if they are unloaded from the weapon before the end of combat. XcomUtil also has an option to let you bring back to base any partly-used clips in weapons.

UFO Redux

It is possible to collect loot from the same UFO two or even three times (similar to "milking" an Alien Base). If you perform a UFO Ground Assault and abort the mission before killing all the aliens, the UFO will have all its aliens and equipment restored, even if you took or destroyed its Elerium. (Bring all captured equipment/corpses back to the transport and unload the alien guns if you wish to recover the clips). If the UFO has another landing scheduled, it will meander around until it reaches its second landing point, at which point you can perform another ground assault. Once a UFO has no further landings scheduled, it will head off at top speed. If you have a fast enough craft, you can shoot it down and perform an additional UFO Recovery on it.

Free HWP Ammo

During base defense, any tanks spawning will get a free load of ammo. (Maybe from X-Com High Command.) If there's any ammo left in the tank at the end of the mission, the remaining ammo is added to your stores! Obviously, this is only useful with the Tank/Cannon, Tank/Rocket, and Hovertank/Launcher. However, it means that tanks make an excellent defense investment, especially if you get free HWP Fusion Bombs out of it. Note that there must be at least one soldier at the base in order to initiate a Base Defense Mission.
Caveat: At the start of the mission, ammo will first be drawn from whatever is in storage. If it's insufficient to arm all of the HWPs, the remainder is what is granted free of charge. To maximise the free ammo, do not stock any ammunition for the defender HWPs. If any are recovered, the ammunition is best transferred to a base stationed with HWPs that actively participate in field batles.

Score Points For Free

Warning: You are crashing the game on purpose.

Works only with the DOS versions of UFO:EU and TFTD

The way this all works is based on the previous tactical in which you went really well and completed it. If the current tactical mission you are on does not go well, press CTRL-C. What has just happened is your current mission has ended with the results of the previous mission. That is, the score, items, corpses, Elerium/Zrbite, and stat increases are carried forward to this mission, from the last. Soldiers will get experience again even if they didn't come on this current mission and are back at base.

What is 'CTRL-C'?
Xcom1 and Xcom2 are DOS games (Disk Operating System, not denial of service). A command used in DOS is "break" which is keyed in as CTRL-C. What this keypress does is halt the current process. Xcom1 & 2 have a failsafe to "crashing" by returning to the previous "good" process, which was a completed tactical mission.

How to Cheat?
Setup: Do a tactical mission with a landed (not crashed) Battleship. Avoid using any weapons that consume ammo (including the tank). Make sure no soldiers die, or tanks. Don't use grenades, flares, etc. Try to do this mission in a 'bean counter' mindset. On the very last turn of the mission (you need to guess it) save your game in a new slot, and then don't overwrite it from here on. Now end the tactical mission normally and continue to play your game normally as well.

Using It:
Later on when you do your next tactical mission and are able to move your guys off the craft, just press CRTL-C. The mission now ends with the results from the Battleship tactical mission. The battleship mission was stored in a folder which is not overwritten when you save your game. It is only overwritten once a tactical mission has been terminated (either from abort, total loss, or from winning). You have just received the score and equipment from a previous mission!


  • If you terminate a tactical mission by accident (by winning or losing - doesn't matter), the results of this current mission will be stored in the "MISSDAT" folder, overwriting the previous tactical mission stored there. To get your Battleship mission back, save the game in your usual spot (you should be back in geoscape view if you have just completed your (accidental) mission). Load the Battleship mission, then end it successfully. The mission results are now refreshed in the MISSDAT folder. Now load your game normally (from the usual spot) and keep playing as per usual. When you next play a tactical mission, just press CTRL-C.
  • If you use this cheat regularly, you'll find that your score goes up very quickly (just like used space in General Stores). Be ready to face more agressive aliens, and more agressive actions (base attacks) from the race of aliens present on that battleship tactical mission.
  • Using this exploit would be best when you still have all the Xcom agents that participated on the original mission. Experience is wasted if most of the agents are dead (it doesn't matter if they are in hospital or at a different base, they'll still get experience), so to get the most benefit from using this exploit, either make new a tactical mission with some of your current seasoned agents, or try not to kill off/sack anyone from the original mission.
  • Big Cheat: Sometimes the icon denoting a crashed UFO/USO does not disappear from the geoscape view after ending a mission using the CTRL-C method (Intact alien craft will take off after the first visit). This means that you can revisit the crash site again and again and rack up a ridiculously large score for the month. If you have multiple multi-role craft (such as the Lightning or the Avenger), then you could have a constant stream of craft visiting the crash site!

Warning: You are crashing the game on purpose.

Due to such drastic methods to cheat, the game may behave strangly (resurrected soldiers, wrong calculations of experience, invunerable crash sites etc.) and it may corrupt files. If you choose to use this exploit, then save you game before you use it, then save your game again IN A DIFFERENT SPOT after you have used it. No one is forcing you to use this cheat, so decide if you want to risk it.

Exploiting Collision Detection

Wall Tile Trick

Most exterior diagonal and some flat UFO walls which occupy the entire tile have faulty boundary definition. A grenade thrown from outside the UFO onto one of these faulty squares will detonate inside the UFO. An unconscious unit thrown onto the same type of square from the outside will wake up inside the UFO once the stun damage has worn off.

Move Through Walls

If an agent is wearing armour which enables vertical movement (see Flying Suit/Mag-Ion Armour) and they are standing under a diagonal overhang, moving up one level will cause the agent to be 'inside' the wall. This agent can now move either way 'through' the wall. However, if an agent does not have flying capability, they can still move through walls if they are on a different level to the wall which you are planning on moving them through.
eg: if you're on a level above a UFO wall (eg: like a barn roof). Move your cursor to a point that is directly above the wall you want to 'stand' in (and eventually go through) and click the mouse button to make your agent move. The agent will walk off the edge, drop down a level (or more), and then step right into the wall. Once your soldier is standing in the wall tile, you can move into the UFO. You could also throw a primed grenade inside the UFO and then step out of the wall to the outside.

Large Units and Different Elevations

Large units use four map cells. The primary quarter, the part that has all the vital statistics and the first part to mind control, is the topmost quadrant (when viewed in tactical view) or the north-west quadrant (when viewed in map view). When moving such units up or down to different map levels (ie: elevations}, mainly via stairs or dropping it off the edge of a wall, the game only uses the primary quarter for collision detection.
WARNING There is a bug which is connected to this exploit. See it here: Faulty Large Units
This faulty collision detection enables large units to move up or down narrow stairs and ramps.

See Through A Ceiling

Agents standing on raised terrain (such as craft ramps, haybales, stairs), do not have a larger sight radius, however, standing on such elevated features raises the agents field of view. This can cause the head of the agent 'pop through' a ceiling and view the floor above when inside a room.

Throw Through Ceilings

All objects can be thrown up through ceilings to land on the floor above. To throw something onto the floor above (even if it that floor has not been scouted yet), just place your cursor on the level above and near your agent and 'throw'. The item or primed grenade will now be up one level (or more) sitting on the ground. Also, since explosions are confined to one level, your agent is safe from any damage from any explosions.

All Terror Missions During Daylight

At night, aliens have a visibility advantage over your soldiers. An Xcom agent can only see so far as the player. Aliens are not limited in any way from the darkness. The Aliens visible distance during a day mission is the same for a night mission. Xcom players obviously would want to do all their tactical missions during the day, however, during the limited time that a terror site is active, daylight may not be an option... not anymore!
When a Terror Site mission appears, save your game, then immediately launch your transport craft as per usual. Once your craft is in close proximty to the city under attack, you'll be able to see if the terror mission is going to be at night or in the day. If it is going to be dark then immediately make your transport craft patrol its current location. However, if you patrol for too long, then the terror site will just disappear and your score will suffer. Do not let the terror site disppear.
Terror Sites disappear on the hour BUT they will not disppear if an Xcom craft (of any sort) is targeting the mission. To take advantage of this fact. Only target the terror mission with your craft (any will do) when the hour changes. Patrol once again for the remainder of the hour, then once again target the terror mission just before the hour changes. If you do this, then you'll be able to stall for time until daylight.
Advanced Tactics:

  • just after a terror mission appears, save your game and let the time pass by at a fast rate. You will see the terror site disappear on a certain hour. This hour is your time limit before you must do something to stop the terror mission from disappearing. Reload your game and try and work out when would be the best time to launch your transport ship to land in daylight hours. Remember, the act of targeting the site will now alter its expiry time. You can keep checking the time it disappears as long as you save/reload.
  • if you guesstimate that you wil NOT win the terror site mission, DO NOT ignore it. Land at the site, then immediately abort the mission. Your score will be pathetic for that mission, but you do not get penalised for ignoring the terror mission outright.

Note: If you want to play every single mission in full daylight, use Scott T Jones's game enhancer, XcomUtil. Just remember that playing in full daylight does remove alot of the suspense. It is almost like cheating.

Grenades: Pass the Experience Trick

(Or who gets the experience when you "drop" a grenade)

Some commanders may have noticed that a soldier that drops a primed grenade rather than throwing it will often not get credited for the damage or killed enemies.

There is a very odd explanation for this. The game attaches an ownership to the grenades. It will rememeber who last threw the grenade so it can credit the right person with experience. Unfortunately, the game only assigns the ownership to a grenade after it has been thrown, but not when it's dropped or picked up.

So who gets the experience if its dropped? All X-COM owned grenades, at the very start of the mission, default to the very first soldier on the transport, or the very first armoured weapons platform if you have one. This means that if a grenade is dropped rather than thrown, all experience goes towards the very first soldier in the list, or the tank.

Can we move the ownership around and pass the experience to soldiers of our choice? Definitely! Just have the person you want to get the experience throw the grenade, then get someone else to carry and drop it to where it can be useful. Just remember to not throw it again.

The method of deployment for these grenades will be left as a practical exercise to the commander. Be creative, or be heartless - it's all up to you!

The biggest advantage of this unusual pass-the-experience technique would be to provide training for frail soldiers that would prove to be more of a detriment in combat than out of it - yet another reason for commanders to not sieve troops based on poor combat statistics.

Mind Control Madness

Civilian Traitors

Whenever you mind control another unit, it automatically returns to the alien side at the end of the aliens' turn. This is true even if you mind control a Civilian. While saving civilians leads to higher scores, "removing" them from play in this way then killing them off as aliens removes the risk of a score penalty should they be fall into trouble.

Resurrect Zombified Agents

also known as: Permanent Control of a Chryssalid/Tentaculat
To 'rescue' your zombified agent you must mind control/molecular control its zombie form then shoot it to make it hatch. The chrysallid/tentaculat that just hatched will appear to be hostile, but don't kill it. Next turn, and for the rest of the mission, it will be controlled by you without additional psionic actions. If you lost an agent to make a zombie and you use this trick, you can 'recover' the agent if the chrysallid/tentaculat version of the soldier survives until the end of the mission. The resurrected agent will be back at base.
If your pet chrysallid/tentaculat happens to get zombified, just repeat the steps to gaining permanent control. This action effectively regenerates your pet's health. However, each time this happens, you lose morale and the counter for the number of X-Com soldiers lost on that mission increases as if it were a different soldier being killed. So you may go in with 10 soldiers, but leave with 10 and -5 casualties.
This exploit can also be used when civilians get zombified. And, since the terror units have many TU, they make excellent scouts. You could give your pet alien a weapon, but they have terrible throwing and accuracy skills. However, if you give you pet a primed high explosive and send them off to scout, they will drop it when they die.

My Pet Alien

Any alien can be your agent's personal escort. Just remember to mind control the alien every turn. When there are large terrorists on a mission, you'll notice that they take up four squares. Each square has its own stats. If you mind control one quadrant, the other three quadrants still stay under alien control. If you move the large alien there is a good chance that it will shoot itself (if it can) via reaction fire. If the large alien does not shoot itself you can use up its TU to fire on hostiles, or use it to scout. Once the TU are used up, mind control another quadrant to keep using this alien. You can do this four times. Alternatively, you can target the other alien quadrants and make the terror unit shoot itself. This is worthwhile tactic to use on Cyberdiscs. They explode on death.

Access the Alien Inventory Screen

When an alien is mind controlled, you can't directly see their inventory by clicking the inventory button. However, if you switch to a human soldier, and check their inventory, you can use the arrows in the top corner to cycle through all units.

WARNING: You will see that sometimes the alien will stack equipment on its right leg. If you remove an item from their right leg, make sure you enough time units to place it somewhere else. If you run out of time units, you will have to force a quit and cannot save your game. (press ALT-TAB, then CTRL-ALT-DEL, and terminate the process that corresponds to the game).

Use this exploit to change their inventory. You can give them weapons (eg: for Reaction Traning}, live grenades, or anything else. Remember to mind control them each turn if you use them as mules.

Exponential Mind Control

Any creature with psionic skill can use a psionic amplifier. Therefore, you can take control of, (eg:) an Ethereal and then toss it a psi-amp, use the alien inventory expolit, and have him pick it up. You can then use the Ethereal's psionic talents to take over other aliens. With the right application of psi-amp relay tosses and mind control, this can have an exponential effect of complete control of all the aliens in the very first turn.


Just how does it work?

NKF quick notes: (I might be duplicating something here, but I'm just jotting these down quickly before I forget)

  • Fire does two types of damage to units. Impact and damage over time.
    • Damage Over time: Standing in fire or actually being on fire.
    • Impact damage: The weirdest and most unusual damage of all.
      • Anyone standing in fire: Receives hit-point damage every time an incendiary shell explodes
      • Anyone standing in smoke: Same as above, but take stun damage instead of hit-point damage.
  • Fire does a fixed amount of damage. The damage of an incendiary weapon only determines how large the spread of the fire will be. So an autocannon incendiary shell is just as powerful as an incendiary rocket -- the only difference is the blast area.
  • Fire and Smoke use the same object table, and being limited, can get used up very quickly and attempts at producing more fire or smoke will not work. Incendiary impact damage will still work on any units in fire/smoke.

JFG adds: Please see my Incendiary topic

Fog of War Scouting

The 3D cursor shows the terrain inside it, regardless of whether you have explored the tile or not. While the obscure shapes shown don't mean much to novice players, veterans will soon recognise tiles, and then the map segments they are native to. For example, you can easily find a UFO by looking for the destinctive wall patterns, and the power supply in the center. Or, you could use this to bombard locations such as command centers, or places you know aliens spawn at the beginning of play, with early Blaster Bombs.

Dead Man Switches

Grenades will only detonate when they are on the ground and when their timer has counted down. Timers will continue to count down regardless of location, but if the grenade is not on the ground, it will not explode. This means that you can set all the grenades to a time of "0" at the beginning of play, or at an earlier turn, and throw them when it's tactically feasible.

This is a double-edged sword, however, because should a unit fall dead or unconcious the grenade will hit the ground and promptly take out anything in the near vicinity... which may (or may not) work to your advantage. This tactic encourages keeping your troops far apart. If you anticipate the soldier will have a very high chance of being killed, it may be wise to use the "pass the experience" trick as described earlier before handing the soldier an armed grenade.

Proximity mines can be defused by saving, quitting the game, restarting it then reloading the game. You can still drop on top of them with a flying suit, or by dropping from a hole in the roof in order to safely pick them up.

Base Defence Mission Spawning Issues

If there are too many soldiers and/or aliens in too small a base, their initial spawning is unusual. Soldiers can spawn in the Access Lift and Hangars. Aliens can spawn outside the Access Lift and Hangars. Some lifeforms may not spawn at all.

Why does this happen? Each base facility has certain hardcoded spawn tiles. The Living Quarters, for example, have 8 spawn tiles, 7 on the lower level in an "H" pattern, and 1 on the upper level. Soldiers usually spawn at these spawn tiles, semi-randomly outside the Access Lift and Hangars. Aliens are assigned the spawn tiles within the Lift and Hangars.

But, if the number of soldiers exceeds the number of "friendly" spawn tiles, the excess soldiers will spawn at the "alien" spawn tiles inside the Access Lift and Hangars. Similarly, if the number of aliens exceeds the number of "alien" spawn tiles, the excess aliens will spawn at the "friendly" spawn tiles in the rest of the base. If there are not enough spawn tiles for the sum of soldiers and aliens, then some lifeforms will not spawn at all. Soldiers have higher spawning priority than aliens, so aliens will be the first to go (fail to spawn). All weapons and items will still be generated, though.

This can be exploited by garrisoning a base with so many soldiers that all spawn tiles are used up. Zero aliens will spawn (but their toys will still be generated), resulting in a bloodless victory and millions of dollars of loot!

A radar base with one Large Radar or HWD, an Access Lift, and one Living Quarters, can be filled up with 22 soldiers.

But if this is considered an exploit, then what is the "ethical" thing to do? To get all aliens to spawn properly at a radar base, you would have to go out of your way and build a hangar. This would in turn affect your defence tactics, and cost you money. If you don't build the hangar, you need to recruit at least 25 armed soldiers (with the accompanying Living Quarters and General Stores), or else a Sectopod or Chrysallid will probably spawn behind friendly lines. At that point, you could argue that the computer is the one doing the cheating, and 25 soldiers seems excessive for a radar base. On the other hand, you would be fighting a reduced number of aliens, since the Access Lift only has 8 spawn tiles.

Maybe you should just shoot down the scouts.

Base FacilitySpawn Tiles on Lower / Upper Floor
Access Lift5 / 3
Hangar15 / 0
Alien Containment7 / 5
General Stores7 / 4
HWD or Large Radar5 / 1
Lab or Workshop6 / 1
Living Quarters7 / 1
Missile Defence4 / 5
Defences (non-missile) or Shields5 / 1
Psi Lab7 / 3
Small Radar0 / 2

Elevator Shielding

Due to questionable AI, aliens will not fire at you through an elevator (either up or down), even though they can see you and you can see them. When approaching elevators, have a soldier stand on it at the end of the turn, even if this leaves them with no TU. The aliens will not be able to come up/down through the elevator, keeping you safely shielded while you bring up rear troops and prepare for a floor breach. Additionally, soldiers may be able to see aliens standing at/near the elevator above or below them and can fire on them from the safety of their "elevator shield".

Milking Alien Bases

This experience training exploit relies on the "Elevator Shielding" exploit. When assaulting an alien base, your soldiers will be deployed at two staging areas with a 2x2 elevator in each one. Block all eight elevator squares with a soldier and wait for the fun to begin. Just keep skipping your turn and eventually, the aliens will find your soldiers and begin to congregate under the elevator. You can now shoot at them with complete impunity and can even pick out specific soldiers who need Accuracy training. When you see that no more aliens are appearing after a few turns, get your solders onto the evactuation area and leave. The alien base is intact for you to return for additional practice later. If you happened to kill everyone the base will be destroyed, so watch the timing of the alien movement phase and take care not to kill everyone. However, the alien leader or commander will almost always stay in the command center, so this is usually not a problem. For best results, arm your soldiers with pistols to maximize the number of shots they can take on each alien. Also, it is not recommended to attempt this tactic on a Sectoid base unless you are very confident of your soldiers' psi strength. As an extra bonus, you can collect alien weapons and equipment before evacuating.