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The Luxtructosaurus is a gigantic hostile boss mob that can be summoned from a volcano in the Primordial Caves. It causes nearby other volcanoes to erupt, has a powerful stomp attack that can level terrain, and can enter an enraged state that grants it the ability to breathe flames in addition to creating fissures in the ground with its stomp.

Cave Compendium Entry

"The Luxtructosaurus is a monstrous boss locked deep inside the heart of the volcanoes that appear within the Primordial Caves. This immense creature is the reason why many dinosaur species that once called the Primordial Caves home have gone extinct. It is an undead dinosaur that is immune to fire thanks to its soul being trapped in the core of a volcano for countless millennia. To awaken this boss and trigger the eruption, one must toss an Ominous Catalyst into the top of a volcano. The Luxtructosaurus has an arsenal of powerful attacks. It can rear up and slam with its front legs, smashing entire layers of blocks into nothing. It can also kick forwards with these legs, sending targets flying. When close to a target, it can spin around and use its long tail to fling targets and disable shields. Occasionally, the Luxtructosaurus will roar loudly and channel the power of the volcano itself to aid it in its battle. This will make the dinosaur drip lava, and it gains the ability to spew flames, along with making its other attacks even more devastating. In this state, the stomp attack of the dinosaur can even expose massive rifts under its targets [sic] feet, full of Primal Magma. If a Luxtructosaurus cannot reach its prey, it can leap great distances or smash blocks in its way. During the entire boss fight, the sky will become red and thick with volcanic ash, and volcanoes will begin to erupt by spewing out flying tephra. This makes the fight even more difficult. In the unlikelihood that the Luxtructosaurus is defeated, it will fade into ash and leave behind multiple Tectonic Shards. Once this great beast is defeated, the Primal Magma left behind will begin to recede and a species of dinosaur previously extinct to the Primordial Caves will instantly begin to spawn from Amber Monoliths. The Tectonic Shards can be used to create the ultimate weapon of the Primordial Caves: the Extinction Spear. This spear channels the spirits of dinosaurs consumed by the eruption long ago. When a target is stabbed with it, the spirit of a Tremorsaurus will lash out and deal additional damage. When held down, multiple spirits of the Grottoceratops will surround the user and block incoming damage. If the spear is thrown and hits a target, a Subterranodon spirit will lift it up into the air and drop it. The spear also deals additional explosive damage in an area after launch, and will return to its thrower afterwards."

- Dr. Prof. Alexander Caverns, PhD.


The Luxtructosaurus is spawned by dropping an Ominous Catalyst onto an active Volcanic Core. When the difficulty is set to Peaceful, it will immediately despawn.


On death

Item Roll Chance Quantity (Default) Quantity (Looting I) Quantity (Looting II) Quantity (Looting III)
Grid Tectonic Shard.png Tectonic Shard 100% 7-11 7-12 7-13 7-14


When the Luxtructosaurus spawns, the sky will turn a deep red and fill with ash, and a unique battle theme will begin to play. In addition to this, all Primal Magma blocks that are paired together will transform into their molten variant, and all active Volcanic Cores will start launching 4-5 fragments of tephra that vary in size and deal explosion damage in addition to creating flaming pools of Primal Magma upon hitting the ground - if a player is within 400 blocks of a Volcanic Core, it will directly launch tephra towards them.

The Luxtructosaurus will attack any players, Subterranodons, Vallumraptors, Grottoceratops, Tremorsaurus, Relicheirus, Atlatitans, or Tremorzilla within a staggering 256-block radius. If another mob attacks its torso, it will retaliate against them, remaining hostile until they die or exit its detection range - being a multi-part mob, the Luxtructosaurus will not start attacking if hit anywhere else. When idle, it will continuously wander around in a random fashion, making loud thumping noises and shaking the screen for all players on the ground within 20 blocks of it as it walks - it will expel red smoke from its nostrils every so often in addition to grunting occasionally. As well as this, it will make not make any attempt to avoid obstacles, destroying any trees it touches in addition to turning any water into stone (unless /gamerule mobGriefing is false). Due to its size, it can step up 3 full blocks without having to jump. If it is below full health and there are no targets within sight range, it will start passively regenerating health.

As a dinosaur, the Luxtructosaurus is able to stand on dinosaur eggs without trampling them.


When fighting targets, the Luxtructosaurus will use any of the following attacks:

  • Kick: When close to its target, the Luxtructosaurus will quickly kick at a target with its left or right front leg, dealing 10♥♥♥♥♥ damage to all targets within 5 blocks in front of it.
  • Tail Whip: When close to its target, the Luxtructosaurus will curl its tail sideways before pivoting around and swinging it at a target, dealing 12♥ × 6 damage to all targets within 12 blocks to the side it swung its tail and disabling shields upon direct hit.
  • Stomp: When within 4 blocks of its target, the Luxtructosaurus will rear up while raising its front legs and bellowing before slamming them back down on the ground, dealing 14♥ × 7 damage to all targets within a 10-block radius in addition to causing the screen to violently shake for all players on the ground within 20 blocks. If on uneven terrain, it will crush all blocks within a 12-block radius, forming a crater up to 6 blocks deep if the terrain is uneven enough - the Luxtructosaurus is capable of crushing all kinds of blocks except barriers, bedrock, command blocks, End portal blocks, End gateway blocks, jigsaw blocks, lights, moving pistons, reinforced deepslate, structure blocks, and Volcanic Cores. If /gamerule mobGriefing is false, this attack will not crush blocks.
  • Leap: When within 5-250 blocks away from its target, the Luxtructosaurus will crouch down before leaping towards them, dealing 6♥♥♥ damage to all targets within range upon direct hit in addition to causing the screen to violently shake for all players on the ground within 20 blocks. After performing this attack, the Luxtructosaurus will be unable to perform it again for a minimum of 5 seconds.

Enraged state

When more than 4 blocks away from its target, the Luxtructosaurus will occasionally wave its head skywards to roar after a minimum of 5 seconds, entering its enraged state for 25 seconds upon doing so - if further away from a target, it will have a higher chance of roaring. Any mob within 64 blocks of the Luxtructosaurus - with the exception of Tremorsaurus, Tremorzilla, or other Luxtructosaurus - will quickly run away from it for 1.5 seconds when it roars; the Luxtructosaurus' roar will also summon 9 fragments of tephra that fall from the sky directly above it in addition to causing the screen to violently shake for all players on the ground within 20 blocks of it. When in its enraged state, the Luxtructosaurus will take on a fiery appearance with a molten chest, tail, spikes, dewlap, and lips, a dark brown, bloody nasal crest, partially molten eye sockets and ear pits, fiery red eyes, and black teeth, in addition to dripping molten saliva from its mouth and gaining the following abilities:

  • Tail Whip: The Luxtructosaurus' tail will emit pyroclastic flames during this attack, setting targets on fire for 10 seconds upon direct hit.
  • Stomp: The Luxtructosaurus' stomp will create fissures filled with Primal Magma 4 blocks deep in the ground over a 48-block radius. Blocks that cannot be crushed by its stomp will also prevent fissures from being created through them. If /gamerule mobGriefing is false, this attack will not create fissures.
  • Flame Breath: The only new attack the Luxtructosaurus gains in its enraged state. When more than 4 blocks away from its target, it will lower its head to the right and open its mouth before breathing out a stream of pyroclastic flames while sweeping its head from side to side for 3 seconds, dealing 3♥♥ damage to all targets within 5-18 blocks away from its front and setting them on fire for 10 seconds every half a second in addition to spreading fires. After performing this attack, the Luxtructosaurus will be unable to perform it again for a minimum of 10 seconds.

If below 25% health (150♥ × 75), the Luxtructosaurus will immediately roar regardless of distance from its target, staying in the following enraged state until it reaches 25% HP or dies - in the former occurrence, it will exit its enraged state after the usual 25 seconds.

Resistances and weaknesses

Being an undead mob, the Luxtructosaurus is:

The Luxtructosaurus is immune to fall, suffocation, fire, lava, and burning damage, and takes 100% less knockback in addition to 35% less damage from non-Tremorzilla dinosaurs, 50% less damage from Iron Golems, and 75% less damage from Wardens; in addition to this, it takes 55% less damage from projectiles that hit its torso and 67% less damage from those that hit anywhere else. Upon initially taking damage, it will take 65% less of any further damage for 10 seconds.

Due to its own ability to roar, the Luxtructosaurus will not run away when a nearby Tremorsaurus or Tremorzilla roars. As a boss monster, it also cannot be possessed by the Totem of Possession.

Death sequence

Upon death, the Luxtructosaurus will enter its molten form and raise its head skywards while wailing, dissolving into ash and leaving behind its drops after 5 seconds - during this sequence, the sky and music will turn back to normal. Items dropped by the Luxtructosaurus have a glowing white outline, similarly to mobs affected with Glowing.

After the Luxtructosaurus dies or despawns, or the chunk containing it is unloaded, tracts of terrain destroyed by fragments of tephra as well as fissures from its stomp will quickly regenerate. Below is a list of blocks that can regenerate from the Luxtructosaurus' attacks once it is removed from the world.

Once the Luxtructosaurus is slain for the first time, a message in yellow saying "New forms are taking shape within Amber Monoliths..." will appear. This refers to a "migration" event that promptly happens for the next day, during which all Amber Monoliths in those Primordial Caves will spawn Atlatitans.


1.1.0 Introduced.
1.1.2 Fixed a bug where it would randomly teleport while moving.
1.1.3 Fixed a bug where it would be neutral towards players.
Fixed an unfinished texture on the top of its front legs.


  • The Luxtructosaurus is conceptually similar to the zombified Argentinosaurus from the Primal animated series, being an undead dinosaur that viciously attacks everything in sight - similarly to its animated series counterpart, it also occasionally leaps on prey. However, whereas the zombified Argentinosaurus was only aggressive enough to chase the protagonists through a volcano, the Luxtructosaurus has full control over volcanic activity.
  • The “-truct” in the Luxtructosaurus’ name comes from “obstruct” (block) - thus, “Luxtructosaurus” can be translated as “light-obstructing reptile”, which accurately reflects the dinosaur’s great size and ability to darken the sky with volcanic activity.
  • The Luxtructosaurus is one of the few mobs in the mod to be animated with inverse kinematics - its legs will shift upwards or downwards to appear as if they are always touching a block.
  • The Luxtructosaurus was conceptualized for Alex's Caves during the same time as all the dinosaurs added to the mod on launch - however, it was held back since Alexthe666 was uncertain about adding it, due to its massive scope. In the end, it was added in a post-launch update.
  • The Luxtructosaurus was the first boss added to Alex's Caves, and is currently the only one in the mod.
    • In extension, it is currently the largest and strongest monster in the mod (the Tremorzilla does not count since it is classified as a creature), as well as the only one that can be encountered in the Primordial Caves.
  • During the months leading up to the launch of Alex's Caves in 2023, Noonyeyz had tricked the majority of the Alex's Mods Discord userbase into believing the Luxtructosaurus was a Spinosaurus-like theropod, going as far as teasing false concept art for it. It was not until the mod's launch that its true nature as a sauropod was hinted at via cave paintings hidden in the files - sometime after, these cave paintings were added to the mod in version 1.0.5, and the "concept art" circulating around the server was revealed to be a hoax.
  • During the Luxtructosaurus' concept phase, it was planned to be able to summon minions to help it fight. Some ideas for the Luxtructosaurus' minions included Baryonyx-like dinosaurs, palaeodictyopteran-like insects referred to as Incendisects, and flaming skeletal cavemen with clubs and spears - one idea even involved it summoning the "eruption" dinosaur variants. All of these ideas were later scrapped due to having been deemed too annoying.
  • The Luxtructosaurus' Cave Compendium entry is a secret entry, and will not appear in Cave Compendiums obtained in Creative.
  • The Luxtructosaurus has the most sounds out of any mob in the mod, at 30 different sounds.
    • The code indicates that, at some point, the Luxtructosaurus was meant to have "snorting" sounds, presumably for expelling smoke from its nostrils - however, they do not appear to be listed in the language files or the sound JSON file, so it is unknown whether they are still planned to be added or were fully scrapped.
    • The Luxtructosaurus has unused sounds for its flame breath - it is unknown when they will be added.