Spider, Giant Trapdoor

ECOLOGY

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)

Added:

• 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