In a combat game, with everything else considered such as basic attack damage, the attacker's strength, the victim's defense and resistance, and anything else that may modify the damage, a same attack will always do the same damage to the same enemy. Either that, or the game doesn't use a damage formula to begin with.
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This, however, is when an attack doesn't always deal the same damage every time - it highly depends on your luck.
In some games (notably RPGs), even normal attacks have a range of values as their base damage. The idea is: No two strikes are ever the same. Maybe you hit a previous injury, or an armored part of the monster, something that's subject to the gameplay's conservation of detail. For games like these, only examples where an attack has a particularly wide range of damage values should be listed here.
Note that this doesn't just apply to attacks - it may be buff spell, defensive technique, even healing - so long as its effects vary depending on random chance.
The Gambler class usually will have many attacks of this property as part of their gimmick.
- Crackle in Hearthstone is a Shaman spell from Goblins vs. Gnomes that costs 2 Mana with 1 Overloadnote that deals somewhere between 3 and 6 damage to a single target. At worst, it's a more expensive Darkbomb, and at best it's a cheaper Fireball. It's one of the most hated cards to see against Aggro Shaman decks because it lets them squeeze in a cheap win for a low cost right before they lose steam, and Aggro Shamans hate using it because it can fizzle and cost them the match.
- Shamans also have Lightning Storm and Elemental Destruction, which have a damage range of 2-3 and 4-5, respectively. While RNG is aplenty in Hearthstone, these are the only examples of randomized damage values.
- In Arcana Heart, a character using Saligrama will get a dice attack where the damage is of course randomized and can sometimes get a buff if you're hit, you hit your opponent or you take fatal damage.
- In the Super Smash Bros. series, Mr Game & Watch's side special attack (called "Judgement") does random damage AND random effects ranging from Mr Game & Watch damaging himself through various Status Effects to smashing the opponent off the map for a One-Hit Kill. Which effect you get corresponds to the number above his head.
- Dofus has a gambling class in Ecaflips who have moves that deal damage randomly between a minimum and maximum base damage amount. The majority of their skills have random base damage, and are themed around gambling themes like card games, slot machines, and coin flipping. Some of their skills even heal the enemy back a small amount to add to the gambling theme.
- In Elsword, Trapping Ranger's Fatality skill can deal either massive, medium, low or Scratch Damage in one hit.
- Perhaps one of the biggest complaints about World of Tanks is the RNG involving nearly all aspects of a shot. Guns generally display their average damage when viewed in-game. Actual damage can vary by 25% in either direction and a string of low damage rolls can seriously hamper a player, especially at higher tiers as average damage and variance increase.
- Phantasy Star Online 2 has the Meteor Fist Photon Art for the Knuckles weapon. This is a chargeable attack that causes golden fists to rain down on your foes. How the fists manifest vary by chance; you can get one small fist, a rain of small fists, or one gigantic fist that does absurd damage. However, the attack needs to be charged in order to see the giant fist at all. There's a reason why it's also called "RNG Fist" by players.
- Dota2: Every unit from the heroes to creeps has attack damage that has a variable so damage is always dealing between minimal or maximum damage. Chaos Knight takes this Up to Eleven where he not only has the most extreme damage variable (-15/+15 compare to most heroes's -3/+3 at average) but also has Chaos Bolt, which inflicts a random but inversely-related amount of damage and stun. Upgrading the spell increases both the maximum and minimum values of both the damage and stun, but there's still a big difference between a 275 damage skill that stuns for 2 seconds, and one that does 100 and stuns for 4.
- Dawn of War: Damage values for some units (especially orks) are all over the place, though this is less the damage and more the accuracy being random.
- Kingdom Rush: Vengeance has the Orc Shaman tower. At maximum level, the basic damage from their lightning strikes ranges from a measly 35 to a huge 190.
- The old DOS game Wizard's Castle deals consistent damage with physical weapons, but the magic spell Fireball deals between one and fifteen points of damage, fifteen being enough to One-Hit Kill any adversary. Similarly, the Web spell will render an adversary unable to strike for as few as one turn to many as five turns.
- In BoxxyQuest: The Gathering Storm, Katy has an attack that deals a random amount of damage to every enemy on the field. At the end of her sidequest, she gives Catie a reusable item that does the same thing.
- Brave Hero Yuusha: The Charge attack, which "Deals random damage to one enemy."
- Chrono Trigger: Lucca has the Wondershot that deals random damage.
- Epic Battle Fantasy gives Natalie the Lucky Star spell, which is cheap on MP, but its damage varies wildly-it can range from a mere tickle to damage highly devastating for such a cheap spell. 3 onward gives her Star Shower, a multi-hitting Area of Effect version of the spell.
- Weapons in the Fallout series generally have a damage range listed in their stats.
- In several Final Fantasy games there's a high-level spell called "Comet" or "Meteor" with a huge variability in its damage output — it could do 100 points damage one turn and 9999 the next, when other spells are more consistent from one use to the next.
- In Final Fantasy VI, Setzer's dice weapons do entirely random damage which is only affected by his level. The game rolls either two or three six-sided dice (depending on the weapon), then multiplies their face values together along with Setzer's level to get the final damage. Doubles and triples multiply the damage further. Since the enemy's defense isn't considered, these weapons are best used against enemies with exceptionally high physical defense such as Cactuars.
- Cait Sith's Dice Limit Break in Final Fantasy VII, which rolls several dice and then inflicts damage equal to the result multiplied by 20 to one enemy.
- In Final Fantasy IX, Quina's normal attack does random damage which is either pathetic or higher than any other physical attacker. This makes him/her a capable (if unreliable) Fighter-type character, but his/her specialty is Blue Magic anyway.
- In Final Fantasy X, Wakka's Attack Reels overdrive deals as many hits as the number you line up in a quick slot reels Mini-Game. This can add up to quite a bit or be barely anything at all depending on the player's reflexes.
- Axes and bombs in Final Fantasy XII vanilla do random damage unless you score a Critical Hit, that consistently deals devastating damage. That, and the fact that most of the better varieties of each weapon are hard to come by, make them not viable for much beyond experimentation and Self Imposed Challenges.
- The Chance Hit ability in Lufia: The Ruins of Lore does fixed damage between 20 and 200, ignoring defense. It can be learned when your physical characters are doing about 30 damage with a standard attack, and won't be topped by your main attackers until late in the game.
- In Mega Man Battle Network series, NumberMan.EXE's Dice Bomb deals damage based on the number on the top side of the dice.
- The move Magnitude has a power between 10 (Magnitude 4) and 150 (Magnitude 10).
- The move Psywave also does random damage; specifically it deals a random number between 0.5x and 1.5x the user's level.
- Present does variable damage, in particular with a chance to do negative damage (i.e. heal the opponent).
- Some moves, such as Fury Attack, Pin Missile, Bullet Seed and others, deal normal damage with each hit but hit a random number of times. This is negated if the user has the Skill Link ability, when they'll always hit the maximum amount of times (usually five) unless the opponent faints before all of them hit.
- In Super Mario RPG, enemy attacks have no random variation of damage, but the player's attacks do. The variation depends on the weapon; unarmed attacks have no randomness, whereas the Masher and Lazy Shell have a very large random factor.
- The Trust mechanic in Valkyrie Profile works effectively like this. Overall potential damage is calculated by a weapon's power and the strength stat of the user, but then there's a variable that gets multiplied in based on the Trust rating of the weapon (with each trust point equal to 1%). A weapon with 100 trust will always do its maximum potential damage, while a weapon with 25 trust can do anywhere between 25% and 100% of its maximum potential damage. Worth noting is that the Infinity +1 Sword has a 1 trust - it's quite capable of doing Scratch Damage even at the end of a massive combo with a Finishing Move.
- Warhammer 40,000:
- This game has several weapons with random strength or random amount of hits, usually determined by D6 or D3 roll. Examples include Chaos daemon weapons (random amount of hits) and Ork zzapguns (random strength). The most extreme example is probably the Dark Eldar Casket of Flensing, which has random range, random amount of shots and random strength.
- Weapons with situational damage also exist, but are much rarer. The conversion beamer, a rare weapon available to certain Space Marine characters and Inquisitors, deals more damage the further away the target is, while the pulse submunition cannons of the Tau R'varna battlesuit increase in strength and amount of hits as the target's size increases.
- In Advance Wars, Flak's CO power randomly makes his units do a lot more more damage or a lot less. His Suspiciously Similar Substitute Jugger has the same ability. Nell and her kid sister Rachel have a variant on this - their CO powers give their units a chance to do quite a bit more damage than usual, but without the "sometimes your hits will suck" part.
- In the old X-COM titles, the weapon stats displayed in game show average damage. Guns roll from 0 to 200% of that, while explosives roll 50-150%. Lucky soldiers can survive point-blank heavy weapons fire while unlucky ones die to stray pistol rounds.
- The "Damage Roulette" Second Wave option for XCOM: Enemy Unknown changes all attacks save for explosives, psionics and MEC subsystems (flamethrower, Kinetic Strike Module and Electro Pulse) so they can can deal between 1 damage and 150% of the max base damage. A Critical Hit will deal the weapon's base damage plus what the regular attack would cause, so they're especially powerful. Which means your soldier can be tickled by a Sectopod's chest cannon, or someone with Titan armor can be one-shot by a lucky crit from a Muton with a plasma rifle that hurts as much as a non-roulette Sectopod cannon shot.
- Problem Sleuth: The Catenative Doomsday Dice Cascader is a machine that uses a process of dice-rolling to determine the damage it deals. First, a central die is rolled to decide how many of the six others will be rolled to determine the actual damage. All the selected dice are then rolled, and each result is multiplied by the previous total to determine the sides of the next die (for instance, if the central die rolls a six and the second one a two, all further dice have twelve sides; if the third rolls an eight then all further dice will have ninety-six sides, and so on). This can end with a final die with a monstrous number of sides, which is then rolled to determine how much damage is dealt to the target. The Cascader is used in a non-canon strip against the Midnight Crew, ending with a final die with over fifty trillion sides. It rolls a one.