Impossible Difficulty (EU2012)

Making the transition from Classic to Impossible can be a steep climb. Here is a comparision of the main differences between both difficulty modes.

Tactical

• XCOM soldiers start with base 3 HPs (and +1 from Body Armor), a reduction that will have effects during all missions but making them very susceptible to KIAs from Sectoid Plasma Pistols at game start.
• The aliens will deploy on bigger numbers (usually 1 additional pod) during the 1st mission and specially on Terror Sites/UFOs. It can be a challenge to know how many pods are still inactivated.
• The AI will use grenades more, specially when facing Muton Elites or Heavy Floaters. After the aliens start fielding grenades the full cover positions in most maps will be very risky to use, since it will be blown away.

General Warnings

1. Missions at the beginning of each month are the most dangerous since usually new aliens will be introduced. April will bring Floater, Mutons (initially equipping with LPRs) in May, Cyberdiscs come in June and Beserkers in July. August brings Heavy Floaters, and Sectopods and Muton Elites will start appearing in September.
2. Expect several of the alien heavy units on the same mission. Terror Sites with 5 Sectopods can be pretty terrifying.
3. Staying out of enemy Line of Sight (LOS) is crucial for the survival of XCOM soldiers. If they are seen they will be fired upon, grenaded and poisoned, and usually killed by a single plasma shot, specially in the first months.
4. During Abductions/Terror Sites/UFO missions the aliens will have a number of packs tied to certain locations while others will be patrolling across the entire map. During the beginning of the mission and depending on the map you may expect to have those packs activated right in front of you.
5. When there are no active aliens, good map knowledge is crucial to know the possible locations of inactive alien packs.

Don't Panic

Panic management can be one of the biggest pains during the starting months on Impossible. The 2 Abduction missions that take place will leave the 4 unattended countries with a level 5 panic meaning that those 4 countries will leave the project at the end of the month. There are two main methods of dealing with this issue:

• Let It Ride - build only 1 satellite during March and launch it over the country that offers the biggest funding or to be able to secure a continent during April. This is the usual method if you are planning to do an April Base Rush strategy, where the main goal is to assault the Alien Base as quickly as possible for the panic reduction and the loot.
  • Advantages - You'll be able to use the credits to get the OTS/Foundry/Alien Containment up and running and advance through your research or get some squad upgrades or S.H.I.V.s quickly.
  • Disadvantages - Your funding will not increase much in April, forcing you to sell a lot of alien artifacts later on. You risk losing one or more useful continent bonuses.
• Satellite Of Love - build 3 sats before March 10th and get 5 engineers as quickly as possible before the 16th to build the 2nd Satellite Uplink. This allows you to cover 3 countries with sats and reduce their panic and, if you are lucky, a Council mission will take place in one of those level 5 countries, meaning 0 defections on March. This method is usually the first step into the Satellite Rush strategy, where the main goal is to get at least 8 satellites on orbit as quickly as possible.
  • Advantages - a lot of needed credits in April and keeping most or all options available regarding continent bonuses for later on.
  • Disavantages - you'll need §200 by the 10th to pay for the sats and an additional 6 engineers by the 16th. While it is easy to get the credits, it's also possible not to get an engineer reward on the 1st Abduction mission, sending this plan crashing back to Earth. And even with the first engineer award, the 2nd Abduction mission may not happen before the 16th, but to anticipate that possibility you can always try building a Workshop as quickly as possible. All of this means that there will be few credits left for any squad upgrades.

Make Your Own Luck

You lost a key Abduction mission or got 0 engineers, failed to capture an alien on time or got a Bomb Disposal Council mission and decided to skip to prevent getting trashed by Thin Men. Things went wrong, either by bad luck or mistake and you were too late to complete a necessary step of any of the previous strategies.

Start responding - cut your losses by cancelling satellites you won't be able to launch (you should always build them in batches of 1 for this purpose) and spend the money elsewhere. Think about what you need to do to get two satellite uplinks up in April, such as workshops, power and excavation. Or reinvest the cash in to squad upgrades and start thinking about what you need to take down the Alien Base at the end of April as a substitute for launching satellites. Or both, since it is even possible to build the second uplink and hit the base if you play your cards right.

Above all, don't panic - losing 3 countries in March isn't catastrophic; no continent bonus is indispensable and you can live without 7 countries as long as you stabilise things before losing the 8th. As they say, sometimes it is necessary to sacrifice a few to save the rest. And remember this definition of luck: "to be prepared when the opportunity presents itself".

Know The Map

Some maps are specially dangerous on Abduction missions, due to their openness, small size and/or general lack of full cover:

• Boulevard Euro
• Cemetery Grand
• Commercial Street
• Demolition
• Fast Food
• Highway Bridge
• Museum Euro
• Pier A
• Rooftops Const
• Small Cemetery
• Street Hurricane
• Street Overpass
• Train Station

Other Abduction maps are more favorable, with much better cover, more movement options and/or easy roof access.

• Bar
• Commercial Alley
• Convenience Store
• Gas Station
• Industrial Office
• Liquor Store
• Office Paper
• Research Outpost
• Slaughterhouse A
• Trainyard
• Truckstop

Take Cover

1. Hunkering behind full cover is the key to survive, specially on the first missions.
2. If your soldiers in full cover can be seen by the aliens, hunker down. It will give them a total of +80 Defense and reduce a Sectoid's chance of hitting to 0 without range bonuses.
3. Only go on Move, overwatch or Fire if that soldier can survive the return fire from any active aliens with LOS on the soldier.
4. Learn which cover cannot be removed by alien gunfire or explosives. Destructible cover can give a very wrong sense of protection and get soldiers killed.
5. Pull back whenever outnumbered, specially right after two or three alien packs activate all of a sudden.
6. If your rookie is feeling brave and sure of hitting with 65% odds, consider what may happen when that alien(s) is still alive after he/she misses:
   1. A single Alien that needs 2 shots to kill one of your soldiers is a nuisance.
   2. 2 or more Aliens that need 2 shots to kill one of your soldiers are a threat. The same for 1 Alien that only needs 1 shot and has your soldier on its sights.
   3. 2 or more Aliens that need only 1 shot to kill a soldier is risking disaster for the entire squad.

Move Softly

1. When scouting with a unit starting on a location in full cover, don't advance to the maximum of moving range during the 1st Action. That way you'll be able to go back, not to your starting location in view of any aliens, but to a square next to it, that prevents the aliens to have Line of Sight in your unit.
2. If choosing between spending the 2nd action to move to full cover or to hunker down behind half cover, go for the latter. Hunkering down gives you +40 Defense (like full cover) and prevents critical hits (unlike full cover).
3. Move very, very slowly when you're sure to approach the location of aliens, either active or inactive. In many occasions it is better to only have 1 unit moving on each turn. This allows to have the entire squad prepared to deal with any hostile encounters.
4. Roofs are essential to move without alien interference. Be aware that some alien packs may be waiting for activation on roofs, though.
5. Aliens overwatching are more deadly: a Sectoid can kill a Rookie when firing on Overwatch, and LPRs can kill Sergeants, if they are not carrying vests.
6. Advancing through dashing will usually result in:
   1. The activation of further alien packs.
   2. Your soldier missing the shot and/or not killing the alien.
   3. Your soldier being killed by the reaction of any active aliens.
   4. All of the above.

Strike Efficiently

1. When a soldier reaches a full cover position where it is overflanking an alien but the odds don't ensure a kill, Hunker Down or go on Overwatch. With the last option, the alien will usually 'freeze' (technically this is a bug/exploit and doesn't work 100% - and doesn't work at all in Enemy Within after the bug fix) and will not take any action during its turn, as long as all XCOM units on its Line Of Sight (LOS) are in full cover.
2. Cars will blow up when hit by a Rocket or two Frag Grenades and add an additional 6 Damage points to any aliens huddled against them.
3. Besides the Damage they inflict, Frag Grenades and Rockets can be used to remove any cover and leave the aliens exposed. Firing at an unit that just got exposed by an explosion gives the attacker a +20/40 Aim boost (depending whether the alien was behind half or full cover), plus a +50% bigger chance to inflict a Critical Hit.
4. One key ability is to be able to kill all or most of a alien pack before or when it's activated, through Rockets, Grenades or Overwatch shots.
5. The longer you take to kill the last active alien, the likelier the odds of an passive pack being activated and forcing you to pull back.
6. Keep a close eye on the squad's ammo levels. If a soldier or the squad is not engaged in combat have all of them reload their weapons. Reload to 100% ammo before activating an alien pack.
7. Splitting up, except for maybe one flanker, is not a great idea, especially since you double the risks of activating alien squads early.
8. If you've managed a good Blitzkreg, and have killed two of an alien squad's members in one round; the AI package for Impossible makes aliens fight more defensively, and will often make the remaining alien panic and retreat with both actions, even if they had a flanking advantage.

Squad Equiping

1. When equipping during the initial months, the choice is between grenades or Nano-Fiber Vests. The first means the ability to remove cover, and weaken/kill single or clustered aliens. The second the ability to survive a single Plasma Pistol or LPR shot.
2. Completing the Slingshot Missions not only gives you early access to the OTS but also to a Lieutenant Heavy and the ability to capture the Plasma Rifle from the Mutons that appear during the missions. You can also capture a Thin Man you get his LPR which allow you to skip the Phoenix Cannon and Laser Cannon completely by going straight to the Plasma Cannon – Just remember that none of the missions give Panic Reduction as a reward, and the rewards are static and not affected by the Second Wave option High Stakes.

• Zhang is considerably better than any other heavy of his rank with his health surpassing that of a Colonel Heavy.

Classes

• The Heavy is the best starting class because of the Rocket Launcher and the Bullet Swarm ability.

1. The Rocket Launcher is a life saver during the first months due to its ability to kill clustered aliens with 1 shot. By adding Shredder Rocket each Heavy can carry the equivalent of two grenades, with even better range and damage abilities.
2. Bullet Swarm is arguably the best second best perk at the beginning. It allows the Heavy to Fire and Hunker Down in the same turn, protecting it from alien counterfire.

• Snipers are also very useful if they have Squad Sight, allowing them to fire without being exposed to the aliens.
• Assaults need to be carefully used. Run & Gun allows to outflank and Overwatch aliens but long dashes can provoke the activation of more aliens.
• Supports are underpowered until Laser Rifles or LPRs are available.

1. The Assault Rifle has a limited damage and critical chance ability compared to the other classes weapons.
2. The Smoke Grenade can only be used once or twice (if they have Smoke & Mirrors and doesn't give the same protection (+20 Defense) as hunkering down (double, or +40 behind full cover).
3. Sprinter is useful for spotting aliens and running away from trouble.

Aliens

Game Start

• Sectoid HPs are increased to 4 HPs, preventing them from being killed by single Frag Grenade, although a well placed frag can take out the cover of three Sectoids, injure them and then leave them open to the rest of your squad.
• Floaters and Thin Men HPs are increased from 4 to 6, making Assault Rifles even more unreliable at killing them, however, their Aim remains the same as in Classic. Rocket Launchers still give 1 shot kills against both aliens.
• Outsiders have 90 Aim, 10 Defense and 17 Mobility (the same as Beserkers). Be very careful with activating Outsiders on Impossible by mistake - a single one on the loose will wreak havoc amongst your troops with their high Aim and Movement.
• Chryssalids remain the same as Classic but Zombies are the bad news. They have 14 HPs (10 in Classic) and their Damage bonus is increased by 4 (+2 on Classic).

Mid Game

• Muton and Cyberdisc stats remain the same as in Classic.
• Drones HP is increased to 7 HPs on Impossible, 2 more than in Classic, turning them into a bigger nuisance. It also prevents Drones from being killed in 1 shot by suppressing them with a Heavy Plasma with HEAT Ammo and Mayhem.
• Sectoid Commanders HP is increased from 10 to 14 HPs on Impossible. They also have a 35 Will bonus (25 on Classic), allowing them even better odds on Mind Control attempts.
• Beserkers health is upgraded 25% from 20 HPs to 25 and they deal 2 extra points of Damage on Impossible (for a total of 11 base damage).

Late Game

• Muton Elites have +10 Aim (for a total of 100 Aim on Impossible), giving the best accuracy on the game. In addition, their health is increased on Impossible from 14 to 18 HPs, while their Defense remains at +30. This combination of high stats, their Heavy Plasmas and their numbers (just facing 3 can be a nightmare) makes them the most dangerous aliens on all situations.
• Heavy Floaters health is added 2 HPs to a total of 16. Their mobility and bigger usage of Alien Grenades (3 tossing grenades at one soldier with deal 15 points of damage) makes them also very dangerous.
• Both Muton Elites and Heavy Floaters now can't be killed with a single plasma shot that isn't ability enhanced (i.e. Headshot, Shredder, Bring 'Em On) since it will deal a maximum of 15 damage with a critical hit.
• Ethereals have +5 HPs and a 35 Will bonus (25 on Classic), allowing them better odds on Mind Control attempts.
• Sectopods stats remain the same as in Classic. However, you'll face more of them during missions instead of just 1. Sectopods also seem to use more their Cannon to blow terrain.

Enemy Within DLC

• Research times are increased by 70% from Easy/Normal difficulties on the EW DLC, 30% more than the 40% increase that already happens with Classic.
• Muton Elites Health Points have been increased to 18 on Classic (from previous 14) and 20 on Impossible difficulties (up from 18).
• No longer possible to abuse the Overwatch exploit to get aliens to freeze.

See Also

• Alien Stats
• Survival Guide