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 Floaters, Mutons (initially equipping with LPR) in May, Cyberdiscs come in June and Beserkers in July.
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.

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
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 the alien will 'freeze' (technically this is a bug/exploit and doesn't work 100%) and will not take any action during its turn, as long as all XCOM units on its 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.

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.
   1. 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 the 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 crit 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 Grenades, although a well placed frag can tale 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 to kill them, however, their Aim remains the same as in Classic. Rocket Launchers still retain their 'kill with 1 shot' ability against both aliens.
• Outsiders have 90 Aim, 10 Defense and 17 Mobility (the same as Bezerkers). Be very careful with activating Outsiders on Impossible by mistake - a single one on the loose will wreck 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 Cyberdisk 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.
• Bezerkers 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 Elite Mutons and Heavy Floaters now can't be killed with a single plasma shot that isn't ability enhanced (i.e. Headshot, Shredder, Bring Them 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.

See Also

• Alien Stats
• Survival Guide