Impossible Mode is the highest difficulty of Dead Space (2008) and its 2023 remake.

In Dead Space (2008), it provides a more tense, gripping experience than the other difficulties (Easy, Medium, and Hard). It can be unlocked by completing the game on any difficulty level. On Impossible Mode, the player must be tactical, conservative, and careful. However, to ease this discomfort, the player starts off the bat with the last suit you used to beat the game that session, without exiting the game or shutting off the console. If the player exits or shuts off the console, and doesn't beat the game again before starting an Impossible game, they will have to start with the Level 1 RIG. Completing the game on this difficulty yields one reward: the "Epic Tier 3 Engineer" Achievement/Trophy.

In Dead Space (2023), it also can be unlocked by completing the game on any difficulty level. It is harder than any other difficulty (Story, Easy, Medium, and Hard). The difficulty has been somewhat further reimagined and now appears as a counterpart to Dead Space 3's Hard Core mode; the player is given one life: should they die, they must either revert back to the beginning of the game or continue playing on Hard difficulty. Completing the game on this difficulty yields three rewards: the Hand Cannon, the Burnished Suit, and the "Untouchable" Achievement/Trophy.

Differences from standard gameplay

Being the hardest level of difficulty means that enemies hit harder, take less damage, and fewer resources can be found in the game world - every shot and decision counts.

• The Necromorphs encountered on Impossible are similar to those in Hard mode in terms of health and damage, but are more likely to sidestep the player's shots, making precise aiming key.
• Item drops are even more scarce than before; pre-set item pickups yields much less quantities compared to lesser difficulties.
• Most of the time the amount of ammo collected from fallen enemies wouldn't be enough to put down the next. Killed enemies are also less likely to drop an item, so don't expect your ammo to be "refunded" by the Slasher you have just killed.
• Credits, though dropping at a somewhat higher rate than ammo and health, are in disappointingly low amounts, often leaving the player with barely enough money for anything.
• Hits from even standard Necromorphs are dangerous and can tear off huge chunks of health if Isaac's RIG is unupgraded. Be aware of your surroundings at all times.

Preparation

• Impossible Mode is unlocked after completing the game on any difficulty, including Easy! However, it is recommended that you at least play through the game on Hard or Medium before attempting it.
• There is a possible glitch where you start this mode in the military suit. If you finished a New Game+ (Round 2) in a Level 6 Military Suit, then start a new Impossible mode game immediately after without powering off, you may (not 100% chance of success, many report consistent failure) see Isaac wearing the military suit in the opening cutscene.
  • It is recommended keeping a save file just before fighting the Hive Mind for this reason. Defeat the Hive Mind, skip the credits, do not save, and immediately start a new Impossible game. Some steps may not be necessary, but the ones outlined above help maximize potential success.
    • Note: Merely loading a save right before the boss will not suffice. You must begin and play through Chapter 12 (possibly even from Chapter 11) in the suit in order to trigger. See Talk.
  • If you plan to buy one of the DLC suits to beat Impossible Mode, the Tank Suit is your best choice since it can take the most damage.
• Plan ahead. Choose which weapons you wish to use and focus your meager resources only on them; you should know the locations of each weapon Schematic from your prior playthrough. The safety buffer of being able to play around with weapons and see which one you like best does not exist in this mode; misspent power nodes or an insufficient supply of ammo/health packs may hinder progress.

General Strategy

• Learn from your mistakes. If you die, for example, due to the Slasher that pounced on you that was just around the corner and cut you to the floor, think of other ways of approaching the problem rather than running in and bludgeoning it with the butt of your gun.
• Weapon selection. Keep a hitscan weapon like the Plasma Cutter, Contact Beam, or Pulse Rifle due to their accuracy.
  • You may wish to consider using a smaller number of weapons in order to maximize the ammo drops for your guns. However, always make sure you have the gun for the occasion. For example, at least one precision weapon like the Plasma Cutter or Pulse Rifle should be used on Drag Tentacles, and at least one area-of-effect weapon such as the Force Gun or Flamethrower should be used against crowds of enemies or Swarmers. Also, try not to bring the Flamethrower into vacuum areas, or the Ripper into areas where you will be fighting at a distance, as these weapons will become dead weight.
• Stasis. Be fluent in its use, and treat it as a weapon. Practice in lesser difficulty modes to hone effective tactics, like stasing multiple enemies at once. Remember to use Stasis frequently.

Ammo	Ammo per pickup	Stack size	Sell price	Kills per pickup
Contact Energy	1	4	1,000	1
Line Racks	2	6	1,000	2+
Ripper Blades	4	15	900	3
Pulse Rounds	25	100	625	1
Plasma Energy	6	25	600	2
Flame Fuel	25	150	500	1/2
Force Energy	3	15	450	1

• Know what to keep and what to sell. Some item pickups are worth more than others. Judge what is the best use of your inventory space to carry/vend, and act accordingly. The table to the right is sorted in descending order by sell price:
• Health packs. Financially, it is optimal to sell all Med Packs. Use Large Med Packs when you need to restore 5+ health bars.
  • Health is not an issue if the player is cautious and avoids taking damage from enemies. However, most health packs at the beginning of the game are small, so inventory space can be quickly consumed by health packs. Feel free to store them or sell them at the Store.
• Always save. Every time you come across a save station, use it because dying is always a possibility, even to the weakest of enemies.
  • Rotate saves. Keep two or more saves for one playthrough, and alternate between them each time you save. This way, if you end up stuck in one chapter without enough ammunition or health to get past, you have old saves to fall back on, so that you don't lose too much progress.
• Conserve ammunition. If you have decent aim, improvise, and use Stasis effectively with melee attacks in order to save ammunition for when it is needed. You could also reload save files in certain situations where you used too much ammunition.
  • Alternatively, consider avoiding fights by running. Use stasis to run around enemies safely, and briefly defend yourself when you're forced to stop (at a slow door, for example).
  • In order to maximize ammo efficiency, fire in controlled bursts to the limbs, and avoid the ammo consuming secondary fire unless absolutely necessary when using automatic weapons such as the Pulse Rifle or Flamethrower. With precision weapons like the Plasma Cutter, always aim for the limbs of enemies (particularly the legs to topple them and really slow them down) to save ammunition and cause more damage to the target.
  • During the first stretches of the game when you (and your enemies) are still weak, try and utilize the shoot-stomp combo (dismember a leg then stomp until the enemy stops moving), with Stasis for insurance. Regular Necromorphs go down very quickly with this method and the only ammo expended during the process is to shoot off their legs. Be cautious of your surroundings, though.
• The Store. Conserve health and ammo so that you may save credits for late use. Weigh out your needs and wants and prioritize survival. If your gun is nearly out of shots while your health is around medium, buy more ammo.
• Power Nodes. Priced at 10,000 Credits each in the Store, they are expensive. While the prospect of buying Power Nodes to open storage rooms for extra supplies or upgrading your gear to deal more damage sounds good, most of the time the reward isn't worth the 10000 Credits spent to buy the Node itself and may cause disastrous shortages of money when you needed it most.
• The Bench. Prioritize damage upgrades so that fewer ammo is needed to take an enemy down. Also, avoid reloading or healing if there's a Bench nearby and you have spare Power Nodes; upgrading ammo capacity in a weapon or max health in your RIG will automatically restore the ammo clip or health, respectively, saving your precious ammo and health packs.
• Use DLC Suits and weapons to make life easier. Not only they provide a better head start, they are FREE. On a difficulty where spending is crucial such as this, the extra 7000 Credits saved from buying a Pulse Rifle can really save your life.

One-Gun Strategy (Plasma Cutter Only)

In addition to the strategies listed above, the following are for those in an Impossible Run and using the Plasma Cutter only:

• Although counter-intuitive, Impossible Mode is the best candidate for a one-gun run with the Plasma Cutter.
  • It is the best weapon cost/benefit wise for ammo consumption, inventory space stacking, and quantity of ammo to kill per ammo pickup.
  • Plasma Energy is relatively cheap to buy from the store compared to other kinds of ammo.
  • Per shot, the Plasma Cutter deals excellent single-target damage, capable of dismembering limbs within 2 shots when damage is fully upgraded.
  • Due to its secondary fire, the Plasma Cutter is highly accurate, thereby minimizing ammo waste.
  • Owning only one gun greatly improves the rate of Plasma Energy drops from enemies and containers and allows the player to focus upgrades on one firearm.
• Aim for the groin region of Necromorphs so that every shot connects with the body and both legs, doubling the damage per shot. Your ammo consumption will effectively be cut in half.
• The first few chapters of Impossible Mode are actually the hardest in any given run since it takes many shots from your un-upgraded firearm and ammo is scarce.
  • Prioritize damage upgrades so that it would take fewer shots to take down an enemy. Ammo conservation is key.
• Due to the lack of splash damage from the Plasma Cutter, Swarmers are easily one of the biggest threats in the game. It's best to use Stasis to run past the swarm, or throw fire extinguishers or explosive canisters to take out the entire wave.
• You will find ammo for other weapons in your playthrough. Since you will not need them, sell them at the Store for credits to buy Power Nodes and ammo.

Trivia

• In Dead Space (2008), there is no bonus cinematic or extra for completing the game on Impossible mode, bar the Achievement.