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Asteroid Worm

Asteroid Worm CR 22

This titanic worm erupts out of the crater before you, its rocky hide and enormous teeth resembling a planetoid coming to voracious life as it reaches out to engulf you.

XP 614,400
N Colossal vermin
Init +0; Senses blindsight (thermal) 120 ft., blindsight (vibration) 30 ft., darkvision 60 ft., low-light vision; Perception +37


EAC 38; KAC 40
Fort +24, Ref +22, Will +18
Defensive Abilities fast healing 30, impenetrable hide, unstoppable; DR 15/adamantine; Immunities cold, disease, electricity, exhaustion, fatigue, fire, mind-affecting effects, poison, paralysis, petrification, polymorph; Resistances acid 30, sonic 30


Speed 40 ft., burrow 20 ft.
Melee bite +36 (21d6+35 P plus swallow whole)
Space 40 ft.; Reach 50 ft.
Offensive Abilities engulf (DC 26, 21d6+35 B), swallow whole (no damage, EAC 38, KAC 36, 137 HP), thundering trample, trample (21d6+35, DC 26)


Str +13, Dex +0, Con +10, Int —, Wis +7, Cha +0
Skills Athletics +42, Stealth +37 (+47 in tunnels)
Other Abilities capacious gullet, mindless, no breath, supercolossal


Capacious Gullet (Su)

An asteroid worm’s gullet is vast enough for creatures to move around within it even after being engulfed, as if it were a 20-foot-wide, 20-foot-high tunnel. The walls of this tunnel are roughly curved, extending 5 feet wider on each side at a height of 10 feet from the floor. This tunnel can extend as long as the GM wishes but should be at least 40 feet long. Creatures swallowed whole or engulfed are not grappled or pinned and do not take additional damage while trapped, though they are considered entangled due to the unstable and shifting rough terrain.

If the worm takes damage while creatures are inside its gullet, it thrashes reflexively as a reaction, causing all trapped creatures to take 8d8+35 bludgeoning damage, falling prone and becoming staggered until the end of their next turn. A successful DC 26 Reflex save halves damage and negates the other effects of this thrashing.

An asteroid worm is treated as a vehicle if creatures in a vehicle wish to escape it. If its bite attack hits a vehicle’s KAC, the worm makes an Athletics check against the vehicle’s KAC. If the check succeeds, the vehicle is engaged with the asteroid worm (see Vehicle rules). If the check succeeds by 5 or more (by 10 or more if the vehicle is Colossal), the vehicle and any creatures on it are swallowed whole. A trapped vehicle can try to break free as a vehicular action, or trapped creatures or vehicles can try to damage the worm sufficiently from the inside that they can escape or force it to eject them, as normal for escaping being swallowed whole.

An asteroid worm can attack a spacecraft that is flying low to the ground or that has landed, treating a spacecraft as a creature that is four sizes larger and dealing only one-quarter damage to spacecraft and their force fields. It cannot engage or swallow spacecraft larger than Medium size (treating them as Colossal creatures).

Impenetrable Hide (Ex)

The worm also gains immunity to bleed and critical hits, though this immunity can be bypassed on a critical hit with an adamantine weapon. Spells that target the asteroid worm’s EAC have a 50% chance to be harmlessly deflected by its hide, and those that successfully strike it deal only half normal damage and have half the normal effect and/ or duration.

Supercolossal (Ex)

An asteroid worm is far larger than normal for its size category.

Its movement is not impeded by difficult terrain, and it can move through the spaces of other creatures smaller than Huge without impediment (and vice versa). Though its actual size does not increase, it is considered one size category larger for all other purposes, including its reach and the ability to affect creatures with special attacks based on size. It can swallow other Colossal creatures whole. It can grapple any number of creatures as long as no more than one is Gargantuan or larger.

Thundering Trample (Ex)

When an asteroid worm uses its trample ability, it creates a powerful shockwave that can knock smaller creatures off their feet. The worm attempts a single trip combat maneuver and applies that roll against all creatures within 10 feet along the path of its movement. If the result exceeds an opponent’s KAC + 18, that opponent is also staggered for 1 round and 1 additional round for every 10 points by which the check exceeded the opponent’s KAC + 18.

Unstoppable (Ex)

An asteroid worm can always use the charge action, even if its movement is impeded or its path is blocked by another creature (though not if it is grappled). It receives a +20 racial bonus on Strength checks to break or destroy objects and can make one such check as a free action as part of a charge. In addition, asteroid worm’s natural weapons bypass 10 points of damage reduction or hardness (5 points of DR/—).

In addition, whenever an asteroid worm would become nauseated, sickened, staggered, or Stunned”>stunned, it can roll twice on the saving throw and select the better result. Even if affected, it gains a new saving throw each round thereafter at the beginning of its turn to remove the effect, even if the original effect did not allow a saving throw (use the standard save DC for effects of a similar nature). Doing so takes no action. The asteroid worm can make a new saving throw every round, but it can remove only one such effect per round.


Environment outer space (asteroids, moons, and airless planetoids)
Organization solitary

Asteroid worms are titanic predators of the spaceways, known to haunt airless moons and rocky belts of drifting planetoids. They can hibernate for long periods but even in their torpor they remain sensitive to the presence of living creatures and of the potent energies of interplanetary spacecraft. Their enormous rocky mass is virtually indistinguishable from the ores and minerals of their lairs, and creatures and even small spacecraft may fly into their monstrous gullets thinking to find shelter or a hiding place amid the crags and craters of a desolate planetary crust. Asteroid worms require no air to breathe, but after consuming prey the worms and the parasitic mites living in their gullets may produce pockets of cloying fumes or damp vapor that pool within their bodies, forming a crude and generally noxious atmosphere of sorts for those plumbing the depths of an asteroid worm’s interior.

Asteroid worms are omnivorous, subsisting on minerals and energies from decimated starships as well as the organic material of creatures traveling within them. They can continue growing almost indefinitely, and specimens hundreds of feet long and weighing hundreds of tons have been discovered. It is believed that they reproduce hermaphroditically, typically after a particularly abundant spree of consumption, expelling a single rock-like egg into the void to grow and mature.

Newly hatched asteroid worms are similar in size, appearance, and abilities to purple worms, though lacking a poisonous sting and not needing to breathe. Once making planetfall, the larval asteroid worm burrows throughout its new home planetoid, honeycombing the planet with caves and cysts as it seeks vital minerals to fuel its growth and build its rocky carapace.

Section 15: Copyright Notice

Alien Bestiary (Starfinder) © 2018, Legendary Games; Lead Designer: Jason Nelson. Authors: Anthony Adam, Kate Baker, John Bennet, Eytan Bernstein, Robert Brookes, Russ Brown, Duan Byrd, Jeff Dahl, Robyn Fields, Joel Flank, Matt Goodall, Robert J. Grady, Jim Groves, Steven T. Helt, Thurston Hillman, Tim Hitchcock, Nick Hite, Daniel Hunt, Mike Kimmel Marshall, Isabelle Lee, Jeff Lee, Lyz Liddell, Jason Nelson, Richard Pett, Tom Phillips, Alistair J. Rigg, Alex Riggs, Wendall Roy, Mike Shel, Neil Spicer, Todd Stewart, Russ Taylor, Rachel Ventura, Mike Welham, George Loki Williams, Scott Young.