You reach into the pack and your hand closes on something that moves. Thirty-eight legs. A mouth. Then the burning starts, and three days later you still cannot lift your sword arm.
Core Statistics #
| Stat | Value |
|---|---|
| Hit Dice | 1/2 HD* (1–4 HP) |
| AC | 11 |
| AV | 0 |
| HR | +0 |
| FR | 0 |
| FD | 8 |
| Move | 60 ft (20 ft encounter) |
| Attacks | 1 bite: poison only (no HP damage) |
| No. Appearing | 2d4 (1d8) |
| Save As | Normal Man (no class) |
| Morale | 7 |
| Treasure | Nil |
| Alignment | Neutral |
| CR | 1 |
| Size | Small (1 ft long) |
| Intelligence | None (INT 0) |
| XP | 6 |
AC/AV Reasoning #
RC original is AC 9 (descending) = Ascending AC 11. The giant centipede is a small, fast-moving insect. It has no meaningful armor — AC 11 is the base ascending value, essentially representing no protection whatsoever.
- AC 11 — Unprotected. The centipede’s defense is its Small size and fast erratic movement. Characters attacking one must contend with a target the size of a large handspan that moves constantly across irregular surfaces
- AV 0 — No protective structure. The centipede dies from virtually any successful hit
- FD 8 — Tiny creature (–2 from standard 10 base) with negligible mass. Shoving a centipede is trivially easy — any forced movement is effective. This is mostly irrelevant since the centipede cannot meaningfully threaten through FR interactions
Skill Slots (1 total — 1/2 HD, asterisk = 1 special ability, INT 0) #
1/2 HD with asterisk = 1 slot maximum. INT 0 limits all development to innate biological functions.
| Slot | Skill / Ability | Notes |
|---|---|---|
| 1 | Paralytic Venom (innate, special) | The bite delivers a debilitating poison. No HP damage. Full mechanics below. The asterisk — despite having 1–4 HP and essentially no combat capability, the venom makes this creature genuinely dangerous. The asterisk is entirely justified |
The Poison — Complete Mechanics #
Trigger #
The centipede bites any creature that disturbs it. The bite deals zero HP damage to any creature of character size or larger — the centipede’s mandibles are too small to penetrate meaningfully. The danger is entirely the venom.
Save vs. Poison #
Each bite requires the target to Save vs. Poison (standard, no modifier for characters of normal size):
Successful save: No effect. The bite itches and leaves a small mark, nothing more.
Failed save: The target becomes violently ill for 10 days.
The 10-Day Illness — Full Mechanical Effects #
The illness is debilitating, not lethal (against humanoid-sized and larger creatures). For 10 days the victim:
- Movement halved: 120 ft characters move at 60 ft; 90 ft characters move at 45 ft; mounted movement is also halved (the rider communicates the impairment to the mount)
- Cannot perform any other physical action: Combat, climbing, swimming, manual labor, and similar physical activities are impossible
- Can still: Walk (at half speed), talk, cast spells (verbal and somatic components — the RC does not restrict spellcasting specifically, and the illness is physical, not cognitive or muscular in a way that prevents hand movements entirely — DM adjudication), eat, drink, and conduct non-physical activities
“Physical action” interpretation: The RC’s “will not be able to perform any other physical action” is broad. Applied strictly:
- Cannot attack (melee or missile)
- Cannot cast spells with somatic components (requires coordinated physical movement — DM may rule verbal-only spells still function)
- Cannot use Guildsman arts requiring physical coordination (Climb Walls, Infiltration)
- Cannot perform Weapon Mastery techniques
- Cannot perform FR/Wrestling maneuvers
Effectively: The victim is a non-combatant for 10 days. They can walk slowly and advise but cannot contribute meaningfully to combat or physical challenges.
Duration and Recovery #
10 days — this is the RC’s exact figure. The illness runs its full course unless magically cured.
Magical curing:
- Cure Disease removes the illness immediately and completely
- Neutralize Poison (if applied within 1 round of the bite, before symptoms develop) prevents the illness entirely
- Cure Light/Serious Wounds does nothing — there is no HP damage to heal
- Bed rest alone does not accelerate recovery — 10 days is 10 days
Multiple bites: A victim bitten multiple times (by several centipedes in the same encounter) makes multiple saves. Each failed save extends the illness duration by 1d6 days (the additional venom loads the system further). Three failed saves could mean 12–28 days of illness — potentially the entire remaining dungeon expedition.
Effect on Small Creatures #
The RC states the bite is “more effective against very small creatures, such as the birds and insects they eat; such creatures must save vs. poison or die.”
“Very small creatures” means creatures of Tiny size or smaller — birds, rats, large insects, creatures of 1/4 HD or less. For these targets:
- Failed Save vs. Poison: Death (no HP damage — the venom is lethal to small creatures)
- Successful save: Half-speed illness as with larger creatures (DM adjudication — the RC does not specify survival behavior for small creatures that succeed the save)
Campaign application: A party’s animal companions, familiars, messenger birds, and small pets are at death risk from giant centipede bites. This is not flavor — it is a genuine tactical consideration. A wizard’s familiar (typically Tiny) that investigates a centipede-infested area faces potential instant death from a single failed save.
Behavioral Profile #
Trigger — “Disturb to Attack” #
“They do not commonly attack travelers, but will usually attack someone who disturbs them.”
What counts as disturbing:
- Moving through a space containing hidden centipedes (underneath rocks, inside packs, in wall crevices, under debris)
- Reaching into or stepping on centipede territory without checking
- Loud vibration near a resting centipede cluster (a heavy footstep, a slammed door)
- Torchlight disturbing a dark area where centipedes are resting
What does not disturb: Simply being near centipedes that are not in the party’s direct path. The centipede does not hunt large creatures — it feeds on insects and small animals. A party that moves carefully through a centipede area and does not physically contact any may pass without incident.
The pack/equipment risk: The most treacherous centipede encounter is not the visible swarm — it is the single centipede that crawled into a dropped pack, bedroll, or boot overnight. A character who reaches into their equipment in the morning without checking may find one. This encounter requires no attack roll — the centipede bites reflexively (Morale is irrelevant for defensive reflex biting), and the character makes their save.
Morale 7 #
On taking any damage the centipede’s Morale check may cause it to flee. Against a creature of standard humanoid size that is actively fighting back, centipedes will generally flee quickly — their instinct is predation of small prey, not combat with giants.
The Morale 7 implication: A party that actively swats at centipedes (even missing) will cause them to scatter. The centipedes are not committed combatants — they are startled insects reacting to disturbance. Aggressive counter-movement (stamping, torch-waving, loud noise) forces Morale 7 checks and disperses most groups quickly.
Habitat and Ecology #
Preferred habitat: Dark, damp places — dungeon crevices, under rotting logs, in wall cracks, beneath stones in ruins, on the underside of large tree bark. The centipede selects locations where it can remain hidden while hunting its actual prey (insects, small arthropods, occasionally birds and small rodents).
Dungeon concentration: Giant centipedes are one of the most frequently encountered dungeon creatures simply because dungeons provide ideal habitat — darkness, dampness, and abundant small prey (dungeon rats, cave beetles, fungal insects). A dungeon with good vermin populations is a dungeon with centipedes.
No. Appearing 2d4 (1d8): Groups of 2–8 in the dungeon, 1–8 in lairs (crevices and wall gaps they inhabit as semi-permanent residents). These are not organized groups — just several centipedes sharing a favorable habitat.
Treasure Nil: Giant centipedes accumulate nothing. They are insects.
Encounter Notes #
The pack search: The DM should occasionally — not constantly, but occasionally — place a giant centipede in an area the party is about to disturb without looking. The dropped pack. The pile of dungeon debris the party is searching for treasure. The bedroll the character did not shake out. The boot left by the door.
Roll the disturb attack as soon as the character’s hand contacts the space. One bite, one save, 10 days of illness on a failure. This is not a combat encounter — it is a dungeon hazard check. It requires no initiative, no attack roll on the centipede’s part, just the save.
The visible swarm: 2d4 centipedes moving across the floor or wall is a different encounter. Here the party can see the threat and act:
- Simply wait (centipedes are moving, not hunting — they may pass by without disturbing the party)
- Use fire (torches near centipedes cause Morale 7 checks immediately — they flee from heat)
- Carefully move through (DEX-based check to avoid brushing through the swarm without contact)
- Attack (trivially easy — 1–4 HP, no meaningful defense — but risks bites during the melee)
Fire as counter: Giant centipedes hate fire. A torch held low and swept across their path forces immediate Morale checks and disperses most groups. A Burning Hands or similar fire effect in a centipede-infested area kills all of them (1 HP each) and eliminates the threat instantly. Flaming oil in a crevice they inhabit is permanent removal.
The multi-bite scenario: A party asleep in a centipede-infested dungeon area, without setting watches or checking their bedding, may face multiple bites during the night. Each sleeping character is treated as disturbing the centipedes present. Two to four saves before morning — on a bad night, most of the party may be ill for the next 10 days, transforming the dungeon expedition into a desperate retreat.
CR 1 justification:
- 1/4 HD = essentially no combat threat (1–4 HP, AC 11, HR +0)
- The 10-day debilitating illness is the entire danger — and it is genuinely dangerous
- Against a single character who fails their save: 10 days of non-combatant status, potentially destroying the expedition’s timeline
- Against a party of four where all fail saves: the expedition is over
- CR 1 is correct because a prepared party with fire and cautious handling trivially avoids or kills centipedes; the danger is entirely from being caught unaware
