Monster Spotlight: Wrackworms
Chaotic Evil Colossal Outsider
Planar Adventures, pg. 250~251
Thousands of years ago, when the great Rough Beast Rovagug was thrown into the world of Golarion and imprisoned within the Dead Vault, an immense quantity of soil and stone was also thrown in with him. As the ages passed, the humble life within the soil was gradually mutated as it consumed the shed flesh of the Rough Beast until it became consumed with the same entropic cruelty of the fiendish deity. These creatures, the Wrackworms, now slither through the flesh of Rovagug directly and, while they cannot harm the great destroyer, they can certainly annoy him until he writhes in his binds and grinds his bulk against the walls of the Vault to alleviate the itch, casting the worms from his body and unleashing them upon the Great Beyond.
These hideous wormy beasts burrow from world to world, plane to plane to sate their immeasurable appetites for destruction and weave hairline cracks through reality like termites devouring the foundation of a house. They do not need to eat, nor do they truly feel hunger, but everything swallowed up by their house-sized maws is eventually entirely erased from reality, permanently removing just a bit more of the cosmos’ ability to recover from injury. Though they’re as dull as a sack of hammers (Int 3), they instinctually understand their destructive capabilities and work towards unmaking creation with relentless glee.
To this end, they do not possess any spell-like abilities to aid them. What they DO have is a suite of natural attacks and a 30ft reach; their bite deals 4d6+13 damage, their quartet of scything throat-claws extending out and slashing for 2d8+13 damage each, and finally their toxic stinger dealing 2d8+13 damage and injecting its victim with a dose of the Wrackworm’s vile ichor, which swiftly eats away at the body. This poison drains 1d4 Str and Dex from its victim every round for up to 6 rounds, though it mercifully requires only 2 saves to overcome it. Aiding in the Wrackworm’s quest to destroy everything, their Penetrating Strikes allow their natural attacks to flat-out ignore all forms of hardness and Damage Reduction, assuring no creature and no substance will be able to stand up to their assault.
Fighting back against the worms is equally difficult, as their Caustic Ichor sprays out with every successful attack against them, dealing 1d6 damage to the attacker and the weapon they’re using to attack in the first place. This damage ignores 10 points of hardness, assuring the destruction of anything but highly-enchanted weapons and those made from skymetal. This isn’t much of a danger to adventurers planning on taking on a CR 20 monster, mind, as magic items gain +2 hardness per +1 enchantment bonus they have, and so much as a +3 enchantment on a steel sword will negate the paltry 1d6 damage the weapon will take. That doesn’t help the fool in melee with the worm, though, who takes that spray of 1d6 each time they successfully strike the worm with a slashing or piercing weapon.
Not that hitting them is easy in the first place. They have 37 AC and are hidden behind DR 15/Lawful and Adamantine, making it difficult for many characters to hurt them… Including ones that try and bypass their tremendous natural armor. Their Twisting Coils instinctively jerk out of the way of incoming touch attacks, granting them an insurmountable +30 AC versus the first touch attack that targets them each round, so the party’s blaster caster or debuffer had better have a backup plan in place. I recommend having two casters in play, since Twisting Coils can only trigger once per round.
Don’t feel so safe in the back lines, though. A Wrackworm’s Wrack Reality ability lets them chew a hole in the very boundaries separating planes as nothing more than a move action, forming semi-permanent Gates through which they can freely travel, either to another plane or to a nearby location in the current one. See that 30ft reach I talked about? It’s a lie. Their reach is actually a mile, because that’s how far apart on the same plane their impromptu portals can be from each other, and the portal remains open (and can be reached through) so long as the Wrackworm remains adjacent to it. While this portal is in place, the Wrackworm is essentially in two places at once, as its lightning-fast movements allow it to reach through and withdraw its natural weapons and make full use of its attack radius on the other side of the portal, as well.
Of course, if that’s stretching the boundaries of your logistics, the Wrackworm could easily just take a 5ft step through the portal and make a full attack. That’s viable, too. The book even notes that the primary use of this ability in combat is for the worm to engage with enemies that keep their distance. Their only other distance option is throwing up! Once per minute, they can Disgorge Wracked Reality to spray 10d6 Acid and 10d6 bludgeoning damage all over a 50ft cone, transforming that patch of land into a patch of acidic (2d6 per round) difficult terrain as well… which, obviously, doesn’t mean much. If you were trying to flee the worm in the first place, unless you can move more than a mile away from it in a single action, you’re not going to get away. .
You can read more about them here.