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"Maybe cybernetics wasn't such a great idea after all. Look what the demons have done with it. It seems unfair somehow you're not the only guy in Hell with a plasma gun."
― Description in the Doom II manual

The Arachnotron is a monster introduced in Doom II. They make their first appearance in MAP07: Dead Simple, where the player must fight a large swarm of them after defeating a pack of Mancubi.

Physical appearance[]

The Arachnotron is similar in appearance to the Spiderdemon; its body consists primarily of a large brain along with two small arms, that is supported by a metal chassis with four mechanical legs.

The main difference is the Arachnotron is smaller in size, and has large blue eyes by default, which change color depending on the monster's current state (moving, hurt, or attacking). Its brain appears to be less wrinkled than that of the Spiderdemon, and instead of a large chaingun mounted on the middle of its chassis, it has a plasma gun.

Combat characteristics[]

An Arachnotron emits a crescendo-ing mechanical cry (akin to machinery powering up) when spotting a player. When in pain, they will make a low-pitch demonic moan that most other monsters make. Like the Spiderdemon, it has audible footsteps, in their case sounding like buzzing machinery punctuated with occasional electronic crackling.

The Arachnotron is armed with a powerful plasma gun installed on its chassis, which fires quick bursts of yellow green energy. Once the Arachnotron engages an enemy, it will continue to fire until the enemy is killed or moves out of its field of view, or until the monster itself flinches in pain or is destroyed - similar behavior can be observed with the Spiderdemon, Wolfenstein SS and Heavy Weapon Dude.

When this monster dies, its head explodes into a morass of gore as its mechanical body collapses while unleashing an electronically pitched dying tone that resembles failing machinery.

Tactical analysis[]

The multiple bursts from the Arachnotron's plasma shots can be quite devastating. And their habit of continuously firing at their enemy upon first sight of them can make short work on an inexperienced player. Furthermore, their plasma bursts are among the fastest projectiles, and it can obscure the player's vision upon a successful hit. The best course of action is once you see the Arachnotron firing its shots, do not stay at one place. Instead, immediately move out of the way and find cover to stop it from continuously firing.

The basic strategy to take out an Arachnotron is from range. As players are able to read the trail of the Arachnotron's plasma bursts from a distance, this can serve as a good indicator for the player to avoid their shots without taking damage. The rocket launcher is an effective long-range weapon as it takes two-three rockets to destroy an Arachnotron. The repeating shots from the plasma gun can also work wonders as Arachnotrons have a medium pain chance, making couple of initial plasma shots to stun them. Due to their robust health and speed of attack and reaction, melee combat is highly discouraged - in some rare instances, a player with a Chainsaw can get lucky to rapidly reach the creature and start sawing it before it can open fire due to their pretty high pain chance.

While the Arachnotrons' plasma shots are fairly powerful, their projectiles are also wide enough that narrow obstacles like pillars, can sometimes act as excellent cover from their shots. On occasions, should players be forced to take them down from a higher plane, Arachnotrons will repeatedly fire, but their plasma shots will only dissipate on the wall of a high ledge where the player is standing, although this requires the monster to stand close to the wall.

Although they may seem slow, Arachnotrons are actually faster than quite a few of the other monsters and can catch up with the player at an alarming rate. If the player must resort to fighting them at close range, the chaingun can work well. A skilled player can also rely on using the super shotgun to take them down at point blank range. However, this will require players to circle around the monster as it takes two-three-point blank shots to obliterate them.

Because of their sustained, extremely fast rate of fire, they are often more than capable of defeating almost any monster if provoked via monster infighting, especially when multiple Arachnotrons attack; however, stronger enemies like the Mancubus would even out the fight, given that it also displays near identical behavior to the Arachnotron as well having attacks just as potent. A Baron of Hell will usually prevail in smaller battles because of their higher health.

Data[]

Attributes
ID # 68 (decimal), 44 (hex)
Hit points 500
Speed 12 map units per frame
(140.0 map units per second)
Width 128
Height 64
Reaction time 8
Pain chance 128 (50%)
Pain time 6 tics
Mass 600
Bits 4194310
Bits list

1: Obstacle

2: Shootable

22: Affects Kill %

Sprites & sounds
Sprite name BSPI
Alert sound DSBSPSIT
Chase sound DSBSPWLK
Action sound DSBSPACT
Pain sound DSDMPAIN
Death sound DSBSPDTH
Ranged attack
Type Projectile
Speed 25 map units per tic
(875 map units per second)
Damage 5-40
Shots per minute 263
Width 13
Height 8
Sprite name APLS (in flight)
APBX (impact)
Sound DSPLASMA (firing)
DSFIRXPL (impact)
PlasmaHistogram

Damage done by each plasma burst

Shots needed to kill Mean Standard
deviation
Min Max
Player (100%
health, no armor)
5.02 1.09 3 8
Player (100%
health, security armor)
7.16 1.23 5 10
Player (200%
health, combat armor)
17.99 1.97 13 22
Barrel 1.44 0.60 1 4
Trooper 1.44 0.60 1 4
Sergeant 1.80 0.75 1 4
Wolfenstein SS 2.75 0.78 2 5
Imp 3.16 0.86 2 6
Chaingunner 3.61 0.91 2 6
Lost Soul 5.02 1.09 3 8
Commander Keen 5.02 1.09 3 8
Demon 7.22 1.29 5 10
Spectre 7.22 1.29 5 10
Boss Brain2 11.68 1.70 8 16
Revenant 13.90 1.83 9 18
Cacodemon 18.27 2.04 13 22
Pain Elemental 18.27 2.04 13 22
Hell Knight 22.80 2.24 17 28
Arachnotron3
Mancubus 27.28 2.45 21 33
Arch-vile 31.76 2.58 25 37
Baron of Hell 45.16 3.09 36 52
Spider Mastermind 134.41 2.61 128 140
Cyberdemon 179.12 2.55 173 184
  1. This table assumes that all calls to P_Random for damage, pain chance, impact animations, and backfire checks are consecutive. In real play, this is never the case: counterattacks and AI pathfinding must be handled, and of course the map may contain additional moving monsters and other randomized phenomena (such as flickering lights). Any resulting errors are probably toward the single-shot average, as they introduce noise into the correlation between the indices of "consecutive" calls.
  2. Assumes that direct hits are possible, which does not occur in any stock map.
  3. Hardcoded exception to infighting negates damage (excepting indirect damage caused by exploding barrels).

Trivia[]

The Arachnotron's sprites have numerous holes in them.

Appearance statistics[]

In classic Doom, the Arachnotron is first encountered on these maps:

Game ITYTD and HNTR HMP UV and NM
Doom II MAP07: Dead Simple MAP07: Dead Simple MAP07: Dead Simple
TNT: Evilution MAP06: Open Season MAP08: Metal MAP04: Wormhole
Plutonia MAP03: Aztec MAP03: Aztec MAP03: Aztec

The IWADs contain the following numbers of Arachnotrons:

Game ITYTD and HNTR HMP UV and NM
Doom II 15 41 64
TNT: Evilution 29 52 57
Plutonia 68 87 94
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