My friends and I were discussing a meme we saw when our imaginations took us way too far, and now I'm curious about how many Crab Swarms it would take to kill the most efficient Crab Swarm killer, and who the most efficient Crab Swarm killer could be.


You are an adventurer who happened upon some hijinks and now suddenly, you're in the middle of a Crab Swarm apocalypse. That is,

  • You're in the center of a 20sqx20sq (100ft x 100ft) flat square plain;
  • You have one week to prepare;
    • For purposes of this theoretical, you may assume you have any necessary resources in infinite amounts.
  • and, after that week, Crab Swarms begin to appear from all directions in an infinite stream.
    • There is nothing special about any individual Crab Swarm; each is exactly as described.
    • They are all hostile against you, specifically, and will do anything within their crablike powers to murder you.
    • The stream will not be stopped and cannot be halted until you are dead.

Specifically, I am interested in the build of any arbitrary level 20 adventurer (for whom 250 CR4 Crab Swarms would make a CR20 encounter). What are the most effective builds at level 20 for eliminating Crab Swarms and prolonging survival?


Spells like Teleport or maintaining indefinite amounts of Rope Tricks, while technically valid for the definition of prolonging survival, are not in the spirit of the scenario, and shouldn't be considered. Running away is not an option.

By "murder", I don't necessarily believe that killing is required. Simply teleporting them to another Plane via skills like, say, Initiate of the Seventhfold Veil's Violet Veil skill is an equally valid strategy (as well as being hilarious in concept).

I am open to basically any valid Pathfinder solution to this problem, from published books. Psionics, Path of War, whatever, bring it on.

  • \$\begingroup\$ Comments are not for extended discussion; this conversation has been moved to chat. \$\endgroup\$ Feb 7, 2020 at 18:51
  • 7
    \$\begingroup\$ Keep in mind that a Crab Swarm, if used as exactly described, dies out by itself pretty quickly while on a plains. Crab Swarms are aquatic and do not have the amphibious trait, so they can't breath air and will die off by suffocation. \$\endgroup\$
    – T. Sar
    Feb 10, 2020 at 12:09

3 Answers 3


A permanent prismatic sphere

The defender can apply a permanency spell to the prismatic sphere spell so that an area—like the one near the center of the 20-square-by-20-square area—constantly emanates the sphere effect; this takes the defender a whole 3 turns (well within the 1 week allotted for preparation). The first three layers of the sphere effect deal enough damage to destroy the swarm even if the swarm succeeds on all three saving throws.

Since a scroll of prismatic sphere has a price of 3,825 gp and a scroll of permanency that can accommodate prismatic sphere (hence caster level 17) has a total price of 24,625 gp, this can be done much sooner than level 20, and pretty much stops in its little arthropod tracks this seemingly very personal crabpocalypse.

  • 3
    \$\begingroup\$ Since you have infinite money, you could expand the perimeter by using several prismatic walls instead of one prismatic sphere, in turn increasing your maximum Crabs per Round. \$\endgroup\$ Feb 6, 2020 at 14:45
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    \$\begingroup\$ @sideromancer Since this only takes 3 turns, really, what a high-level dude would do is use an effect like contact other plane and ask Where are all these damn crabs swarms going to come from? then going there (probably by teleportation) and using the permanent prismatic sphere that he bought as a cork. Poof! Crabpocalypse never. \$\endgroup\$ Feb 6, 2020 at 14:56
  • \$\begingroup\$ Use the proposed infinite resources to build yourself a wicked mansion in that week-long span and protect it from the crabs, and bam. Living in comfort and forever safe from crabs. Really, though, I had completely forgotten this spell existed, and it definitely is among the most effective possibilities. \$\endgroup\$
    – toki
    Feb 7, 2020 at 0:43
  • \$\begingroup\$ Then you just need a couple other spells (surely easier to cast than Prismatic Sphere/Walls) to sustain yourself indefinitely. Make sure to pick an immortality capstone. \$\endgroup\$
    – Ifusaso
    Feb 7, 2020 at 13:31
  • \$\begingroup\$ @Ifusaso Or just create a simulacrum of yourself in the sphere and just leave. \$\endgroup\$ Feb 7, 2020 at 13:41

Make a bottomless pit

For only 7,000gp you can buy a scroll of Curse Terrain, Supreme. This allows you to lay a Perilous Demesne, Grand onto the ground for a set a bottomless pits around the square.

Since the crabs will walk into it like lemmings jumping off a cliff, the following section of the hazard applies.

Other than its depth, the extraplanar space’s dimensions match those of the pit’s entrance, and the falling creature can attempt to catch itself on the wall, using the Climb skill (DC = 20 + the wall’s Climb DC, as normal for catching yourself when falling), and can attempt to climb out of the pit from there. The wall’s climb DC typically matches the type of terrain the opening was in, so a rocky chasm has a Climb DC of 15, for example.

A crab swarm has 1 strength and 0 ranks in climb, giving it a climb check of -5. This means that it is impossible for them to catch onto a wall and they will be forever trapped in a pit as you sit on your lawn chairs eating popcorn and occasionally tossing some into the pit.

You can then use a scroll of permanency to keep the pits there forever if your crab-apocalypse will last more 15 days for only 29,875‬ gp, giving you a total cost of 36,875gp.

Unlike @Hey I can Chan's answer, you could then install permanent portals around the pit for sending the cab-apocalypse onto the next group of hapless adventurers to deal with as the occasional one falls through.

Note: You really only need Curse Terrain, Greater, reducing the overall cost to 22,525gp, but hey, we've got infinite money, why not use some of it.


It is simpler than it looks!

You need a Carpet of Flying and a Ring of Sustenance.

Sit on top of your carpet, fly up, and wait.

The Crab Swarm is an aquatic creature without the Amphibious subtype. It can't breath on land, and thus will die off by itself in a few turns.

This solution has a combined cost of 22.500gp, or half that if you're allowed to pay the crafting cost.

No special build or class necessary, just two off-the-shelf magic items.


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