The onyx worm's long, black segmented body has a thick, crystalline carapace. These worms spend most of their life burrowing through earth and stone in search of crystalline deposits for nourishment, though they also have been known to surface and attack psionic creatures. Sounding like rolling thunder, an onyx worm's sonic attacks can resonate for miles underground.
While the true motivation for their attacks on psionic creatures is unknown, some believe that the worms have a need to ingest psionic creatures as part of their reproductive cycle. Dwarven miners have reported finding entire colonies of crysmals completely decimated in areas where they heard the thunderous sounds of an onyx worm only days before. These worms often seek out neothelids and engage them in a battle that can last for days, though the combat often results in the death of both creatures.
Onyx worms are relentless in combat, and they pulverize their foes with their body and constant mental and sonic assault. While they usually use their psionic abilities for movement and borrowing purposes, some have even been known to use them in combat, as well.
Breath Weapon (Su): Once per hour, an onyx worm can release a sonic energy attack in a cone shape similar to a breath weapon. The cone has a length of 80 feet and causes 15d6 points of damage (Reflex half DC 22). Creatures in the area of effect of the breath weapon are also psionically assaulted by a mind blast (psionic combat mode); psionic creatures can defend as normal. An onyx worm is immune to its own breath weapon.
Psionics (Sp): At will -- body equilibrium, levitate, improved telekinesis, true metabolism; these abilities are as the powers manifested by a 18th-level psion.
Attack/Defense Modes (Sp): At will -- mind blast*, mind thrust*/intellect fortress. An onyx worm's mind blast attack is part of its breath weapon. Mind thrust is part of its sonic blast and death throes. The area of effect of these attack modes is the same as the attack instead of that as listed in the Psionics Handbook. The creature can use these attack modes only in conjunction with the listed abilities.
Sonic Blast (Su): Once per round, an onyx worm can release a blast of sonic energy that affects all creatures within 20 feet for 3d6 points of damage (Reflex half DC 22). This blast can be delayed. If delayed, the blast becomes more intense and increases by 3d6+3 points of damage per round. It also expands in size by a 10-foot radius per round. The blast can go up to a maximum of 12d6+9 points of damage and a 50-foot radius. Creatures in the area of effect of the blast are also psionically assaulted by a mind thrust (psionic combat mode); psionic creatures can defend as normal.
Death Throes (Ex): When killed, an onyx worm explodes with one final sonic-based explosion that sends shards of crystal in all directions. The explosion deals 12d6 points of sonic damage and 8d6 points of piercing damage to everything within 60 feet (Reflex half DC 22). Creatures in the area of effect of the explosion are also psionically assaulted by a mind thrust (psionic combat mode); psionic creatures can defend as normal. The crystal shards have no value but are often mistaken for onyx.
Tremorsense (Ex): An onyx worm can automatically sense the location of anything within 60 feet that is in contact with the ground.
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