Spider, Giant Trapdoor

Giant Trapdoor Spider CR 4

XP 1,200
N Large vermin
Init +2; Senses darkvision 60 ft., tremorsense 60 ft.; Perception +4


AC 15, touch 11, flat-footed 13 (+2 Dex, +4 natural, –1 size)
hp 37 (5d8+15)
Fort +7, Ref +3, Will +1
Immune mind-affecting effects


Before Combat A giant trapdoor spider lies in wait in its hole for potential prey to wander by for hours or days at a time.

During Combat The spider lunges out at anything of size Small or Medium that disturbs its web trigger lines. It seeks to grab its prey as quickly as possible and pull it back into its hole to consume in safety. If it is not able to pull a creature into its hole within one round (either during the surprise round or the first full round of combat) it withdraws into its hole for safety. If it is not holding a meal it uses its strength to hold the trapdoor closed, increasing the DC to lift it from 25 to 29.


Speed 30 ft., climb 30 ft.
Melee stabbing bite +6 (1d10+6 plus attach), consuming bite +1 (1d4+3 plus poison)
Space 10 ft.; Reach 5 ft.
Special Attacks surprise strike


Str 19, Dex 15, Con 16, Int —, Wis 10, Cha 2
Base Atk +3; CMB +8 (+16 to maintain grapple); CMD 20 (32 vs. trip)
Skills Acrobatics +10, Climb +12, Perception +8, Stealth +4; Racial Modifiers +8 Acrobatics, +8 Climb, +8 Perception, +8 Stealth


Attach (Ex)

When a giant trapdoor spider hits with its stabbing bite attack, its scimitar-length mandibles penetrate the target, holding it fast. An attached giant trapdoor spider is effectively grappling its prey. The giant trapdoor spider loses its Dexterity bonus to AC and has an AC of 13, but holds on with great tenacity. A giant trapdoor spider has a +8 racial bonus to maintain its grapple on a foe once it is attached. An attached giant trapdoor spider can be struck with a weapon or grappled itself—if its prey manages to pin the giant trapdoor spider then they may remove it.

Consuming Bite (Ex)

A giant trapdoor spider consumes its food with a secondary, smaller set of mandibles. These teeth are less pronounced than their larger, stabbing mandibles but possess a weak toxin in addition to the lesser damage they deal. A giant trapdoor spider generally does not attempt to use its consuming bite attack until it is safely within its burrow, away from other potential enemies or creatures which might attempt to steal its meal. This is a secondary attack.

Weak Poison (Ex)

When a giant trapdoor spider hits a creature with its consuming bite attack it injects a weak toxin which slowly paralyzes the victim.

Consuming Bite

injury; save Fort DC 15; frequency 1/round for 6 rounds; effect 1d3 Str; cure 2 saves. The saving throw DC is Constitution-based.

Stabbing Bite (Ex)

A giant trapdoor spider has a large set of curved, scimitar-length mandibles it uses for digging its tunnel and as its primary attack form. When attacking, it attempts to stab prey with these mandibles, holding them fast while it drags them into its hole to devour with its consuming bite.

A giant trapdoor spider may make one stabbing bite attack during the surprise round against a size Small or Medium target within 10 ft. of its hole. If this attack is successful it immediately backs into its tunnel to consume its prey. Re-entering the hole automatically causes carefully placed webs to trigger the trapdoor to close behind it, separating itself and its prey from any other creatures, allowing it to consume its prey safely.

Sudden Strike (Ex)

A giant trapdoor spider lays carefully hidden trigger webs in a 10 ft. radius around its hole. If a size Small or Medium creature comes enters this area it may make a free DC 24 Perception check to notice the trigger threads. If successful, the creature notices several fine threads on the ground. A successful DC 19 Knowledge (nature) check will reveal their true nature and purpose, as well as what lurks nearby. If the Perception check fails and the creature steps into the area it will momentarily find itself stuck to one or more trigger webs. These lines break quickly and easily but not before alerting the spider that it is now mealtime. The ground suddenly springs open as a 10 ft. tall horrifying spider lunges out towards whatever stepped into its trap.

A giant trapdoor spider may make one stabbing bite attack during the surprise round against a size Small or Medium target within 10 ft. of its hole. If this attack is successful it immediately backs into its tunnel to consume its prey. Re-entering the hole automatically causes carefully placed webs to trigger the trapdoor to close behind it, separating itself and its prey from any other creatures, allowing it to consume its prey safely.


Environment warm temperate
Organization solitary, pair, or colony (3–8)
Treasure incidental

Giant trapdoor spiders are especially aggressive, nearly hairless Large spiders that construct burrows with a cork-like trapdoor made of soil, vegetation and silk. They have powerful jaws and vicious fangs that stab downwards into prey. Giant trapdoor spider venom, while still a threat, is a relatively weak threat compared to their bite.

A giant trapdoor spider prepares its tunnel and trap so that it is as difficult to notice as possible. It takes 20 on its Stealth check to conceal its tunnel, resulting in a DC 24 Perception check being required to notice the circular crack outlining the opening or possibly the web trigger lines.

Opening the Trapdoor

Lift: The trapdoor is anchored in place by its own weight, some amount of webbing, and the spider itself hanging from its underside. Attempting to lift the trapdoor requires a DC 25 Str check (the combined weight of the spider, soil, and webbing being between 500-700 lbs.) If the spider is not inside the tunnel reduce the DC of the Str check to 18.

Cut Through: Chopping through the trapdoor is potentially a faster and easier solution. It is usually about a foot thick consisting of dirt, vegetation, and matted webbing. The trapdoor has hardness 3 and 60 hp per 5 ft. section (there are roughly 4, or enough sections to cover a 10 ft. by 10 ft. round hole.)

The trapdoor is difficult to see when it is closed because the plant and soil materials effectively camouflage it. The trapdoor is hinged on one side with silk. The spiders, which are usually nocturnal, typically wait for prey while holding on to the underside of the door with their claws. Prey is captured when they disturb ‘trip’ lines the spider lays out around its trapdoor, alerting the spider to a meal within reach. The spider detects the prey by vibrations and, when it comes close enough, leaps out of its burrow to make the capture. A Giant trapdoor spider has very large rake-like appendages on their mandibles which are usually used to dig their tunnel but make for especially lethal weapons against their prey.

A hungry individual will wait halfway outside of its burrow for a meal. They use their pedipalps and first legs to hold the trapdoor closed when disturbed.

Females never travel far from their burrows, especially if they have an egg sac. During this time, the female will capture food and regurgitate it to feed her spiderlings.

Encounter Options

This encounter is too weak!

Add spiderlings in tunnel!

If you would like to increase the challenge level of this encounter a bit, add one or two spider swarms inside the tunnel. During the surprise round, while mommy is out getting their food, they are readying to move over whatever she brings back. When a victim is drug into the tunnel, the spiderlings immediately (as a readied action) swarm over it, causing a bit more to be concerned with.

Adding one spider swarm increases the CR of this encounter from 4 to 5 and the XP award changes from 1,200 to 1,600.

Adding two spider swarms increases the CR of this encounter to halfway between 5 and 6 and increases the XP award from 1,200 to 2,000.

Too Tough!

Add a giant wasp!

Giant wasps are natural hunters of trapdoor spiders. They fly about in search of tunnels and then simply chew through the trapdoor. Once through the door they sting the spider, inject it with eggs, then fly away. If you wish to offer your players a bit of an “escape valve” or rather, a way to dial back the threat level a bit, if the spider is having its way with a PC perhaps have a giant wasp be overheard buzzing nearby. The player’s will likely react with some degree of nervousness, especially of the encounter is already going poorly. However, when the wasp arrives it zeros in on the tunnel, immediately begins chewing on the “soil” and then engages with the spider, possibly offering the trapped PC or his allies an opportunity to free him, especially of there is now a giant-sized hole in the trapdoor. If the PCs are foolish enough to attack the wasp though, this could quickly turn from an attempt to save their bacon to a TPK (total party kill.)

If you feel it necessary to reduce the challenge of this encounter by adding a giant wasp, reduce the overall CR by 1 and reduce the XP awarded from 1,200 to 800.

Design Notes

Base creature: Giant Black Widow Spider

Removed from base creature:

  • reduced poison DC
  • reduced poison effectiveness by removing staggered effect
  • removed strong webs special quality
  • removed web special attack (it is a hunting spider not a web-spinning spider in classical sense)


  • increased primary bite damage from d8 to d10
  • added secondary, lesser bite
  • added attach monster ability
  • added surprise strike special attack
  • added Acrobatics (it is a hunting spider not a web-spinning spider)
  • corrected Climb modifier based on editor’s notes for giant black widow spider
  • increased Perception & Stealth racial modifiers from +4 to +8 as this is a hide-and-wait style predator
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