Dragon Warrior (nmikstas/dragon-warrior-disassembly)

Dragon Quest (developer Chunsoft, publisher Enix) came out for the Famicom in Japan on 27 May 1986, and Dragon Warrior for the NES in North America in August 1989. dw1/release

Cited by: Critical hit, Dragon Warrior, Fleeing, Hit chance, Random encounter, Turn order

Dragon Warrior's title screen reads "©1989 ENIX" and "LICENSED TO NINTENDO", by the disassembly's comments on the strings' tiles. dw1/title-screen

Lowered from T3 on 2026-10-25: the evidence quoted only the annotator's tile comments. In the Rev 1 CHR bank whose tiles $01, $08, $09, and $24 to $3D match the comments' digits and letters (CHR $1000-$1FFF), tile $62 is a window-border piece, not ©, so the title screen may load other tiles or another bank; an emulator read of the title screen's nametable would settle it.

Cited by: Dragon Warrior

Rev 1 differs from the build of nmikstas's disassembly in three bytes of text and none of code; on its title screen "TRADEMARK TO NINTENDO" becomes "TRADEMARK OF NINTENDO". dw1/rev1-text

Banks 1 and 3 hold all the battle code cited here (bank 3 is fixed at $C000), so every Bank03.asm claim describes Rev 1 too.

Cited by: Damage formula, Dragon Warrior

UpdateRandNum steps a 16-bit state as $s\leftarrow 771s+129(\mathrm{mod}65536)$, and battle code reads its high byte, RandNumUB. dw1/rng

About: Dragon Warrior Random number generator

Cited by: Dragon Warrior, Random number generator, RNG manipulation

GetJoypadStatus steps the generator each time it reads the controller. dw1/rng-joypad

About: Dragon Warrior Random number generator

Ryan8bit's guide adds that an idle menu runs the generator 60 times a second, so a command's outcome depends on when it is chosen.

Cited by: Dragon Warrior, Random number generator, RNG manipulation

Computed from the generator's update, its 65,536 states form two cycles of 32,768, and over each cycle the high byte takes every value exactly 128 times. dw1/rng-cycles

About: Dragon Warrior Random number generator

Because the high byte is uniform, sweeping all 65,536 states gives a routine's exact odds for a uniformly random state, which is how dw-battle.mjs measures every *-measured claim.

Cited by: Dragon Warrior, Random number generator

The hero's attack power is Strength plus the weapon's bonus; defense power is half of Agility, rounded down, plus the armor's and shield's bonuses, plus 2 with the Dragon's Scale. dw1/attack-power

About: Dragon Warrior Damage formula

Cited by: Dragon Warrior, Hit chance

PlyrCalcHitDmg takes $X=A-\lfloor D/2\rfloor$, the hero's attack power less half the monster's defense byte; if $X\ge 2$, damage is $\lfloor (X+\lfloor r(X+1)/256\rfloor )/4\rfloor$ for a random byte $r$, so from $\lfloor X/4\rfloor$ to $\lfloor X/2\rfloor$. dw1/hero-damage

About: Dragon Warrior Damage formula

nmikstas names the monster's second stat byte EnBaseDef; Ryan8bit calls the same byte Agility, because run checks also use it (run).

Cited by: Damage formula, Dragon Warrior, Multi-hit attack

When $X<2$, the hero deals 0 or 1 damage, each half the time. dw1/hero-weak

About: Dragon Warrior Damage formula

Cited by: Damage formula, Dragon Warrior

Zero damage from the hero ends the turn as a failed attack, before any dodge check. dw1/zero-damage-fails

About: Dragon Warrior Hit chance

Cited by: Dragon Warrior, Hit chance

Before the normal formula, a 1-in-32 roll gives the hero an "excellent move", except against either form of the Dragonlord; it deals $A-\lfloor r\lfloor A/2\rfloor /256\rfloor$ for a random byte $r$, from $\lceil A/2\rceil +1$ to $A$ (more than half to all of the attack power), and ignores defense. dw1/excellent-move

About: Dragon Warrior Critical hit

{
 "chance": [
  1,
  32
 ]
}

The excellent move then joins the normal path at SetEnDmg1, so the monster's dodge check applies to it too (dodge).

Cited by: Critical hit, Damage formula, Dragon Warrior

After the damage is set, an awake monster dodges when a roll of 0–63 falls below $d$, the low nibble of its resistance byte, a chance of $d/64$; a sleeping monster never dodges, and spells skip the check. dw1/dodge

About: Dragon Warrior Hit chance

nmikstas's comment at L6796 gives the top chance as "22% (14/63)"; by the code a nibble of 15 dodges 15 times in 64, 23.4%.

Cited by: Critical hit, Damage formula, Dragon Warrior, Hit chance, Multi-hit attack

EnCalcHitDmg takes $X=A-\lfloor D/2\rfloor$, the monster's attack less half the hero's defense power; if $X\ge \lfloor A/2\rfloor +1$, it uses the hero's normal formula, and otherwise the monster deals $\lfloor (\lfloor r(\lfloor A/2\rfloor +1)/256\rfloor +2)/3\rfloor$, from 0 to about $A/6$. dw1/monster-damage

About: Dragon Warrior Damage formula

nmikstas's comment at L8529 writes the weak formula with AttackStat - DefenseStat/2; the multiply uses ⌊A/2⌋ + 1, as Ryan8bit's guide also has it.

Cited by: Damage formula, Dragon Warrior

A monster's physical attack has no critical branch and no dodge roll for the hero; EnPhysAttack goes straight to EnCalcHitDmg, and only 0 damage misses. dw1/monster-no-critical

About: Dragon Warrior Critical hit

Cited by: Damage formula, Dragon Warrior, Hit chance

A monster's HP is its base value less up to a quarter, $H-\lfloor \lfloor rH/256\rfloor /4\rfloor$; the Dragonlord's final form always has its base HP. dw1/monster-hp

About: Dragon Warrior Damage formula

Cited by: Dragon Warrior

The hero's Hurt deals 5–12 damage and Hurtmore 58–65, whatever the stats on either side; a roll of 0–15 below the high nibble of the monster's resistance byte blocks the spell instead. dw1/hero-spells

About: Dragon Warrior Damage formula

{
 "hurt": [
  5,
  12
 ],
 "hurtmore": [
  58,
  65
 ]
}

Cited by: Damage formula, Dragon Warrior

A monster's Hurt deals 3–10 damage and Hurtmore 30–45; Magic Armor or Erdrick's Armor cuts either to $2\lfloor d/3\rfloor$. dw1/monster-spells

About: Dragon Warrior Damage formula

{
 "hurt": [
  3,
  10
 ],
 "hurtmore": [
  30,
  45
 ]
}

nmikstas's comment at L7830 says Hurt does "between 7 and 10"; the code adds 3 to 0–7.

Cited by: Dragon Warrior

At the start of a battle, CalcWhoIsNext gives the hero the first turn when Agility × a random byte is at least the monster's defense byte × a roll of 0–63; otherwise the monster attacks first. dw1/first-turn

About: Dragon Warrior Turn order

Cited by: Dragon Warrior, Fleeing, Hit chance, Turn order

TryRun lets the hero escape when Agility × a random byte is at least the monster's defense byte × a roll whose range grows with the monster: 0–63 from Slime to Druinlord, 0–94 from Drollmagi to Werewolf, 0–127 from Green Dragon to Blue Dragon, and 0–255 from Stoneman on. Running from a sleeping monster always works. dw1/run

About: Dragon Warrior Fleeing

{
 "groups": [
  [
   0,
   63
  ],
  [
   0,
   94
  ],
  [
   0,
   127
  ],
  [
   0,
   255
  ]
 ],
 "firstMonster": [
  0,
  20,
  30,
  35
 ]
}

nmikstas's comments name the groups one monster off (Stoneman is in the last group, not the one before). The first group goes through CalcWhoIsNext, so it draws one byte more than the others and uses the same test as first-turn.

Cited by: Dragon Warrior, Fleeing, Hit chance, Random encounter, Turn order

Measured in the ROM over all 65,536 generator states, with Agility 40 against a defense byte of 40, the hero escapes 87.70% of the time from the first group, 81.64% from the second, 75.20% from the third, and 50.20% from the fourth; the hero takes the first turn 87.70% of the time. dw1/run-measured

About: Dragon Warrior Fleeing

{
 "probe": {
  "run-slime": {
   "states": 57474
  },
  "run-drollmagi": {
   "states": 53506
  },
  "run-green-dragon": {
   "states": 49282
  },
  "run-stoneman": {
   "states": 32898
  },
  "first-turn": {
   "states": 57474
  }
 }
}

Cited by: Dragon Warrior, Fleeing, Random number generator, Turn order

Measured in the ROM over all 65,536 generator states, attack power 60 against a defense byte of 40 deals 10–20 damage, each of 10 to 19 in 25 of 256 rolls and 20 in 6; attack power 20 deals 0 or 1, half each. dw1/hero-damage-measured

About: Dragon Warrior Damage formula

{
 "probe": {
  "hero-normal": {
   "atk": 60,
   "def": 40,
   "min": 10,
   "max": 20
  },
  "hero-weak": {
   "atk": 20,
   "def": 40,
   "min": 0,
   "max": 1
  }
 }
}

Cited by: Dragon Warrior

Measured the same way, a monster's attack of 90 against defense power 60 deals 15–30 damage, and an attack of 20 against defense power 40 deals 0–4, mostly 1–3. dw1/monster-damage-measured

About: Dragon Warrior Damage formula

{
 "probe": {
  "monster-normal": {
   "atk": 90,
   "def": 60,
   "min": 15,
   "max": 30
  },
  "monster-weak": {
   "atk": 20,
   "def": 40,
   "min": 0,
   "max": 4
  }
 }
}

Cited by: Dragon Warrior

At the start of a battle and before each monster turn, CheckEnRun gives the monster a 1-in-4 chance to flee when half the hero's Strength is at least the monster's attack. dw1/monster-flees

About: Dragon Warrior Fleeing

{
 "chance": [
  1,
  4
 ]
}

Cited by: Dragon Warrior, Fleeing

Each step on the map draws a byte and starts a fight when its masked bits are all 0: 1 in 8 on sand and hills, 1 in 16 in swamp, forest, brick, and barrier squares, and on other terrain 1 in 32 where the X and Y coordinates are both even or both odd, 1 in 16 elsewhere. dw1/encounter-rate

About: Dragon Warrior Random encounter

nmikstas's comment at L2040 calls the $1F mask the higher chance; five zero bits are half as likely as four. Towns and other maps without enemies return later, in DoRandomFight.

Cited by: Dragon Warrior, Random encounter

On the overworld's zone 0, the slime-only region around Tantegel Castle, a second byte lets only half of those fights through, and a quarter on hills. dw1/encounter-zone-0

About: Dragon Warrior Random encounter

Cited by: Dragon Warrior, Random encounter

After the first turn, the hero and the monster alternate; each of the hero's actions ends by jumping to StartEnemyTurn, and each of the monster's to StartPlayerTurn. dw1/turns-alternate

About: Dragon Warrior Turn order

Cited by: Dragon Warrior, Turn order

A failed run prints "But was blocked in front" and passes the turn to the monster. dw1/run-fail

About: Dragon Warrior Fleeing

Cited by: Dragon Warrior, Fleeing

The NES manual advises running away when the hero's HP is close to 0, calling it “a very important ‘fighting’ technique”. dw1/manual-run

About: Dragon Warrior Fleeing

Cited by: Fleeing

The NES manual says Agility helps the hero escape: "This means that you can more easily avoid the enemy or run away." dw1/manual-agility

About: Dragon Warrior Fleeing

In the code, Agility enters the run and first-turn tests and the hero's defense power (run, first-turn, attack-power); no roll lets the hero dodge (monster-no-critical).

Cited by: Fleeing, Hit chance, Turn order

The NES manual describes encounters as meeting a monster on the map: "If you happen to bump into one of them, the game will automatically enter the fight mode." dw1/manual-encounters

About: Dragon Warrior Random encounter

The map holds no monsters to bump into; a per-step roll starts each fight (encounter-rate).

Cited by: Random encounter

The NES manual's terrain guide says fewer monsters live on plains, more lurk in forests, and mountains bring "many enemies". dw1/manual-terrain

About: Dragon Warrior Random encounter

The manual's passable "Mountains" are the hill squares of nmikstas's labels (BLK_HILL); its "Craggy mountains" are impassable. The order matches the code's rates, 1 in 8 on hills and 1 in 16 in forest (encounter-rate).

Cited by: Random encounter

The dodge nibble $d$ of the 40 monsters (each dodges $d/64$ of the hero's attacks, dodge) is 1 or 2 for 27 of them; the Demon Knight's is 15, the Werewolf's 7, the Poltergeist's and Drakeema's 6, six monsters' 4, and the Golem's and both Dragonlord forms' 0. dw1/monster-dodge

About: Dragon Warrior Hit chance

{
 "of": 64,
 "byD": {
  "0": 3,
  "1": 12,
  "2": 15,
  "4": 6,
  "6": 2,
  "7": 1,
  "15": 1
 },
 "byMonster": {
  "Slime": 1,
  "Red Slime": 1,
  "Drakee": 1,
  "Ghost": 4,
  "Magician": 1,
  "Magidrakee": 1,
  "Scorpion": 1,
  "Druin": 2,
  "Poltergeist": 6,
  "Droll": 2,
  "Drakeema": 6,
  "Skeleton": 4,
  "Warlock": 2,
  "Metal Scorpion": 2,
  "Wolf": 2,
  "Wraith": 4,
  "Metal Slime": 1,
  "Specter": 4,
  "Wolflord": 2,
  "Druinlord": 4,
  "Drollmagi": 1,
  "Wyvern": 2,
  "Rogue Scorpion": 2,
  "Wraith Knight": 4,
  "Golem": 0,
  "Goldman": 1,
  "Knight": 1,
  "Magiwyvern": 2,
  "Demon Knight": 15,
  "Werewolf": 7,
  "Green Dragon": 2,
  "Starwyvern": 2,
  "Wizard": 2,
  "Axe Knight": 1,
  "Blue Dragon": 2,
  "Stoneman": 1,
  "Armored Knight": 2,
  "Red Dragon": 2,
  "Dragonlord": 0,
  "Dragonlord True Self": 0
 }
}

nmikstas's column label is Mdef; the byte also holds the Hurt resistance in its high nibble (monster-hurt-resist). His row labels read "Metal slime" and "Rouge Scorpion"; the value uses the names from Ryan8bit's list. The Metal Slime's dodge is 1/64, like a Slime's.

Cited by: Dragon Warrior

The high nibble $h$ of the same byte blocks Hurt and Hurtmore $h/16$ of the time (hero-spells); it is 0 for 26 of the 40 monsters and 15 for seven, the Metal Slime, Golem, Demon Knight, Wizard, Red Dragon, and both Dragonlord forms. dw1/monster-hurt-resist

About: Dragon Warrior Hit chance

{
 "of": 16,
 "byH": {
  "0": 26,
  "1": 3,
  "2": 1,
  "3": 1,
  "7": 2,
  "15": 7
 },
 "byMonster": {
  "Metal Slime": 15,
  "Wraith Knight": 3,
  "Golem": 15,
  "Demon Knight": 15,
  "Green Dragon": 2,
  "Starwyvern": 1,
  "Wizard": 15,
  "Axe Knight": 1,
  "Blue Dragon": 7,
  "Stoneman": 7,
  "Armored Knight": 1,
  "Red Dragon": 15,
  "Dragonlord": 15,
  "Dragonlord True Self": 15
 },
 "others": 0
}

byMonster lists the 14 monsters with a nonzero nibble; the other 26 have 0.

Each fight picks one of its zone's five monster slots with equal chance; zone 0, around Tantegel Castle, holds three Slime slots and two Red Slime slots, and zone 1 adds a Drakee, all with dodge 1. dw1/opening-monsters

About: Dragon Warrior Hit chance

{
 "slots": 5,
 "zone0": {
  "Slime": 3,
  "Red Slime": 2
 },
 "zone1": {
  "Red Slime": 3,
  "Slime": 1,
  "Drakee": 1
 },
 "dodge": {
  "Slime": 1,
  "Red Slime": 1,
  "Drakee": 1
 }
}

Zone 0's lower encounter rate is encounter-zone-0.

The Demon Knight, the hardest monster to hit at 15/64, fills one of the five slots in overworld zones 10, 11, and 12; the Werewolf, at 7/64, fills one in zone 12 and in zone 13, which Hauksness also uses, and one on the Dragonlord's castle ground floor. dw1/evasive-monsters

About: Dragon Warrior Hit chance

{
 "Demon Knight": {
  "d": 15,
  "zones": [
   10,
   11,
   12
  ],
  "slotsPerZone": 1
 },
 "Werewolf": {
  "d": 7,
  "zones": [
   12,
   13,
   16
  ],
  "slotsPerZone": 1
 },
 "slots": 5
}

Zone 11 also holds the Metal Slime, whose dodge is 1/64. In OvrWrldEnGrid, zone 12 fills the grid cell just south of one of zone 0's.

The Dragonlord's castle's six sublevels draw from three rows, Werewolf, Green Dragon, Starwyvern, Wizard, and Axe Knight on the first; Wizard, Axe Knight, two Blue Dragons, and Stoneman on the next three; and Wizard, Stoneman, two Armored Knights, and Red Dragon on the last two and the bottom floor. Apart from the Werewolf's 7, their dodge nibbles are 1 or 2. dw1/late-monsters

About: Dragon Warrior Hit chance

{
 "rows": {
  "16": [
   "Werewolf",
   "Green Dragon",
   "Starwyvern",
   "Wizard",
   "Axe Knight"
  ],
  "17": [
   "Wizard",
   "Axe Knight",
   "Blue Dragon",
   "Blue Dragon",
   "Stoneman"
  ],
  "18": [
   "Wizard",
   "Stoneman",
   "Armored Knight",
   "Armored Knight",
   "Red Dragon"
  ]
 },
 "dodge": {
  "Werewolf": 7,
  "Green Dragon": 2,
  "Starwyvern": 2,
  "Wizard": 2,
  "Axe Knight": 1,
  "Blue Dragon": 2,
  "Stoneman": 1,
  "Armored Knight": 2,
  "Red Dragon": 2
 }
}

Rows are numbered from 0 in EnemyGroupsTbl; row 16 ($10) is also the castle's ground floor (evasive-monsters).