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Brontosaurus/Apatosaurus

Gargantuan beast, unaligned


Appearance:
The Brontosaurus is a massive, quadrupedal dinosaur with an elongated neck that arches gracefully toward the treetops, allowing it to browse vegetation far above ground level. Its thick, muscular tail whips behind it, balancing its bulk, while its sturdy, pillar-like legs support its immense weight. Its skin is rough and leathery, mottled in earthy greens and browns that blend with the forest canopy. Despite its size, its small head sports keen, watchful eyes that scan for threats.


Behaviour:
Generally peaceful and slow-moving, it lives in herds that wander vast floodplains and dense prehistoric forests. It is a focused browser, spending much of its day feeding on high vegetation unreachable by most other creatures. When threatened, it uses its powerful tail in sweeping strikes and can stomp with overwhelming force to deter predators. Brontosaurus relies on its size and herd numbers for defense rather than speed or stealth.


Habitat:
Brontosaurus inhabits temperate floodplains, river valleys, and fern-covered woodlands where tall trees provide abundant foliage. These environments offer both plentiful food and safety within the herd. Its large size means it requires vast ranges to sustain itself.


Modus Operandi:
It moves deliberately but steadily, using its height advantage to feed on treetop leaves, rarely descending to ground-level vegetation. It communicates with low-frequency bellows that resonate across distances, coordinating herd movements and warning of danger. When confronted by predators, it stands its ground, wielding its massive tail and powerful legs to protect itself and others.


Motivation:
Survival and the protection of the herd drive the Brontosaurus. It seeks to maintain access to feeding grounds and avoid conflict where possible, but it will fiercely defend its young or vulnerable members. Its motivation is fundamentally instinctual—preserve life, maintain territory, and continue its lineage through the safety of the herd.


  • Brontosaurus 5e
  • Brontosaurus 3.5

Brontosaurus, Thunderous Colossus

Gargantuan beast, unaligned
Challenge: 9 (5,000 XP) • Proficiency Bonus: +4


Armor Class 16 (natural armor)

Hit Points 210 (20d12 + 80)

Speed 40 ft.


STRDEXCONINTWISCHA
25 (+7)8 (−1)18 (+4)2 (−4)12 (+1)8 (−1)

Saving Throws Con +8, Wis +5

Skills Perception +5, Survival +5

Damage Resistances Bludgeoning, Piercing; from nonmagical attacks

Condition Immunities Prone, Grappled, Restrained

Senses Passive Perception 15

Languages

Proficiency Bonus +4


Traits


Titanic Bulk

The Brontosaurus cannot be knocked prone or moved against its will. It ignores difficult terrain and can move over creatures of Large size or smaller without penalty.


Herd Guardian

The Brontosaurus has advantage on saving throws against being frightened while any ally is within 30 feet.


Tremor Walk

Whenever the Brontosaurus moves at least 10 feet on its turn, all creatures within 10 feet of its path must succeed on a DC 17 Strength saving throw or be knocked prone.


Actions


Multiattack

The Brontosaurus makes two attacks: one with its Tail Sweep and one with Stomp.


Tail Sweep

Melee Weapon Attack: +11 to hit, reach 20 ft., one target.
Hit: 29 (4d10 + 7) bludgeoning damage. The target must succeed on a DC 17 Strength saving throw or be pushed 15 feet away and knocked prone.


Stomp

Melee Weapon Attack: +11 to hit, reach 10 ft., one prone creature.
Hit: 36 (6d8 + 7) bludgeoning damage. If the target is prone, it takes an additional 14 (4d6) damage.


Thunderous Bellow (Recharge 5–6)

The Brontosaurus emits a deafening roar. Each creature within 60 feet that can hear it must make a DC 16 Constitution saving throw or take 18 (4d8) thunder damage and be deafened for 1 minute. A successful save halves the damage and prevents deafness.


Legendary Actions

(Optional)
The Brontosaurus can take 2 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature’s turn.

  • Tail Sweep. The Brontosaurus makes one Tail Sweep attack.
  • Seismic Stomp (Costs 2 Actions). The Brontosaurus stomps the ground forcefully. Creatures within 15 feet must make a DC 17 Strength saving throw or fall prone and take 14 (4d6) bludgeoning damage.
  • Move. The Brontosaurus moves up to half its speed without provoking opportunity attacks.

Tactics

  • The Brontosaurus defends itself and its herd with powerful sweeping tail attacks and crushing stomps.
  • It uses Tremor Walk to disrupt enemy formations and keep foes off balance.
  • Thunderous Bellow serves to scatter or intimidate attackers, especially when outnumbered.
  • Typically avoids direct conflict unless threatened or protecting young.

Environment

  • Brontosaurus roams vast floodplains and forested river valleys, moving in herds and shaping the landscape as they feed.
Brontosaurus/Apatosaurus
Outdated 1897 restoration by Charles R. Knight of B. excelsus submerged in water, and Diplodocus dragging its tail

A 40 ton plant-eater found near marshes and lakes. it spends much of its time in shallow water to support its bulk.

Originally Posted by Kain Darkwind of the Dicefreaks d20 Community.
On this Thread

Brontosaurus meaning “thunder lizard” is a genus of gigantic quadruped sauropod dinosaurs.

Brontosaurus has a long, thin neck and a small head adapted for a herbivorous lifestyle; a bulky, heavy torso; and a long, whip-like tail. Adult individuals of Brontosaurus weigh up to 15 tonnes and measured up to 22 metres (72 ft) long.

As the archetypal sauropod, Brontosaurus is one of the best-known dinosaurs and has been featured in film, advertising, and postage stamps, as well as many other types of media.


Brontosaurus
Colossal animal
Hit Dice30d8 + 303 (438 hp)
Initiative+0
Speed20 ft.
Armor Class16 (+14 natural, -8 size), touch 2, flat-footed 16, combat 70
Base Attack/Combat+22/+55
AttackTail +33 melee (4d8 + 29) or Power Attack tail +16 melee (4d8 + 54)
Space/Reach30 ft./30 ft.
Special AttacksTail sweep, trample
Special QualitiesLow-Light VisionScent
SavesFort +28, Ref +11, Will +14
AbilitiesStrength 46, Dexterity 10, Constitution 29, Intelligence 2, Wisdom 12, Charisma 10
SkillsPerception +27, Survival +17
FeatsAbility Focus (tail sweep), Awesome Blow, CleaveEndurance, Great FortitudeGreater Weapon Focus (tail), greater weapon specialization (tail), Improved Bull RushIron WillPower Attack, Run, Skill Focus (Perception), Skill Focus (Survival), ToughnessWeapon Focus (tail), Weapon Specialization (tail)
Climate/TerrainWarm swamps
OrganizationSolitary
Challenge Rating13
TreasureNone
AlignmentUsually neutral
Advancement31-60 HD (Colossal)

Tail Sweep (Ex): As a standard action, a brontosaurus can sweep a half-circle with a radius of 30 feet. Gargantuan and smaller creatures take 2d8 + 25 points of damage. (Reflex DC 44 half)

Trample: 4d12 + 25 damage, Reflex DC 42 half.

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