Sunday, February 15, 2026

Prehistoric Monsters for OD&D

This is the last in a series of posts in which I stat up monsters for original Dungeons & Dragons.  This is necessary work, but not the most exciting blog content.  It's helpful for me, though, as it's given me things to post about without taxing the grey matter too much (and I am very, very tired after indoor bouldering with my son this afternoon, so I need the mental break).  I should be back with some more substantial content next time.  (And I will get to the Martian creatures... eventually.)

The main takeaway for me in regards to the various dinosaurs and prehistoric animals, is that adventuring in their environments has a high level of danger for no reward.  I'm adapting their stats from Advanced D&D, which means that pretty much all of them have a Treasure Type of Nil.  What this means is that I'll have to make these environments worth adventuring in, with treasure deliberately placed.  Hidden ruins and such would, of course, be thematically appropriate.  On their own, purely by the rules, dinosaurs and the like are absolutely not worth fighting.

I like the selection of dinosaurs in OD&D though.  The AD&D Monster Manual has a greater variety, but in OD&D it's pretty much all of the dinos that I would have wanted to see as a kid.  It's a real pop culture greatest hits selection (keeping in mind that the velociraptor wasn't in that upper echelon in the 70s and 80s).

TYRANNOSAURUS REX

Number Appearing: 1-2
Armor Class: 5
Move in Inches: 15
Hit Dice: 18
% in Lair: Nil
Type or Amount of Treasure: Nil

This reptile is the most fearsome and terrible of all carnivorous dinosaurs. Despite its huge size it is swift afoot, with huge jaws nearly six feet long, and teeth from three to six inches in length.  This monster will pursue and eat nearly anything

A T-Rex deals 3d6+3 damage on a successful hit, and will swallow whole any man-sized creature that it hits with a roll of 18 or better.

PTERODACTYL

Number Appearing: 3-18
Armor Class: 7
Move in Inches: 3/15
Hit Dice: 3+3
% in Lair: Nil
Type or Amount of Treasure: Nil
 
Although these flying reptiles typically dive for aquatic prey, they will attack any creature which appears to be vulnerable. They have no teeth, but will spear victims with their beaks if they are too large to swallow.  The beak of a typical pterodactyl is about 4 ft. long. The creature weighs only 40 or 50 pounds, but they can carry off prey four times their own weight.

TRICERATOPS

Number Appearing: 2-8
Armor Class: 2 or 6
Move in Inches: 9
Hit Dice: 16
% in Lair: Nil
Type or Amount of Treasure: Nil
 
This beaked herbivore is very large and aggressive. It has a huge front plate of bone from which project two great horns (3 ft. or more long), while a somewhat shorter horn juts from its nose. Any creature which infringes on its territory is likely to be charged and speared.
 
The armored front of the Triceratops is AC 2.  Its body is not as heavily armored, thus being AC 6.  

Any creature attacked by a Triceratops will be subject to three attacks (the two larger horns dealing 1d6+2 damage, and the smaller horn dealing 1d6).  Creatures of man-size or smaller creatures may simply be trampled for 2d6+1 damage.

BRONTOSAURUS

Number Appearing: 1-6
Armor Class: 5
Move in Inches: 6
Hit Dice: 30
% in Lair: Nil
Type or Amount of Treasure: Nil
 
Also known as a "thunder-lizard", this 40 ton plant-eater is found near marshes and lakes.  The creature spends much of its time in shallow water to support its bulk, moving into deeper water to avoid carnivores.  They will generally ignore small creatures, but they are prone to step on anything in their way, dealing 4d6 damage.
 
STEGOSAURUS
Number Appearing: 2-8
Armor Class: 2 or 5
Move in Inches: 6
Hit Dice: 18
% in Lair: Nil
Type or Amount of Treasure: Nil
 
The stegosaurus, or ”plated lizard,” is a large, very stupid herbivore with aggressive defenses. Its great plates allow the creature to defend 90% of the time at AC 2.  The other 10% of the time it defends as AC 5.
 
When threatened, a Stegosaurus will turn its rear towards the enemy and tuck its head low, attacking with its spiked tail.  The tail has its own brain, and its bony spikes will deal 2d6+1 damage.

CAVE BEAR

Number Appearing: 1-2
Armor Class: 6
Move in Inches: 12
Hit Dice: 6+6
% in Lair: Nil
Type or Amount of Treasure: Nil
 
Despite being omnivorous, the gigantic cave bear tends towards a diet of meat, and is quite aggressive. They have excellent hearing and smell but rather poor eyesight.  They are enormous, standing over 12 ft. tall, but there may be larger individuals that are correspondingly more powerful. 
 
A cave bear's paw deals 1d6+2 damage on a successful hit, and they may attack twice per round.  If a bear scores a paw hit with an 18 or better, it also hugs for an additional 2d6 damage.
 
A cave bears will continue to fight for 1-4 melee rounds after being reduced to 0 to -8 hit points. At -9 or greater damage, they are killed immediately. 

DIRE WOLF

Number Appearing: 3-12
Armor Class: 6
Move in Inches: 18
Hit Dice: 3+3
% in Lair: 15%
Type or Amount of Treasure: Nil
 
This "prehistoric" variety of wolf is a huge specimen, but otherwise conforms to the characteristics of normal wolves.  They always hunt in packs and if hungry (75% likely) they will follow and attack prey, always seeking to strike at an unguarded moment.  They love horse-meat, and their howling is 50% likely to panic any horses (or other herbivores) unless a character spends time calming them.
 
If encountered in their lair there is a 30% chance that there will be 1-4 cubs per pair of adult wolves.  Cubs do not fight and can be trained as war dogs or hunting beasts.

SABRE TOOTH TIGER

Number Appearing: 1-2
Armor Class: 6
Move in Inches: 12
Hit Dice: 7+2
% in Lair: 15%
Type or Amount of Treasure: Nil
 
Sabre tooth tigers are aggressive and fearsome predators, often hunting in pairs.  They are highly adaptable and superb hunters.  They climb well, and are able to leap 10 ft. upwards and from 30 to 50 ft. forwards in attack.

Tigers attack three times per round, twice with claws and once with their bite.  Their six inch long fangs inflict terrible wounds, dealing 1d6+2 points of damage.  Due to the size of these teeth, along with the power of the tiger's jaws, they get a +2 bonus on attack rolls with their bite attack. If a tiger hits with both paws, they will get an additional claw attack by raking with their rear claws.
 
Tigers are surprised only on a roll of 1. 
  
If encountered in their lair there is a 25% chance that there will be 1-3 cubs there, these young having no effective attacks, and being from 30% to 60% mature.

MASTODON

Number Appearing: 1-12
Armor Class: 6    
Move in Inches: 15
Hit Dice: 12
% in Lair: Nil
Type or Amount of Treasure: Nil
 
Mastodons dwell in nearly any climate, from near arctic to tropical. These huge herbivores are distantly related to elephants, but their body is somewhat lower and longer.
 
Mastodons attack with a combination of tusks, squeezing trunk, and stomping feet.  Each of these attacks deals 2d6 damage.  Although they may attack only a single foe twice per round, they may fight up to six opponents simultaneously.  Their attacks are split between opponents, so that if they are fighting six opponents they get one attack on each, and if fighting three opponents they attack each twice.
 
Their tusks are valued at 100-600 gold pieces each.

SPOTTED LION

Number Appearing: 2-8
Armor Class: 5 or 6
Move in Inches: 12
Hit Dice: 6+2
% in Lair: 25%
Type or Amount of Treasure: Nil
 
Also known as cave lions, spotted lions are a larger, spotted variety of the common lion.  They hunt in prides, with the lioness doing most of their hunting.  Even so, the males are ferocious fighters and will defend the pride's territory.  A typical pride consists of 1-2 males and 1-6 females.  Their lair will also have 1-8 cubs (non-combatants) and an additional 1-3 females which will immediately attack to defend their cubs.
 
All lions can leap up to 30 ft.  Male lions have an AC 5 for their forequarters, and AC 6 for their hindquarters.  Female lions have a uniform AC of 6. Lions attack twice per round, and if both attacks hit the same victim in a single round they will also rake with their rear claws for a further 1-6+2 damage.  They do not climb trees well and dislike swimming.

Lions are surprised only on a roll of 1. 

WOOLY RHINO

Number Appearing: 1-4
Armor Class: 5
Move in Inches: 12
Hit Dice: 10
% in Lair: Nil
Type or Amount of Treasure: Nil
 
A very large, very aggressive "prehistoric" species of rhinoceros.  Most will charge if they feel threatened.  They have poor eyesight but keen senses of hearing and smell.
 
They deal 1d6+2 damage with their horns, but will deal double damage on a charge. They will also trample any opponent smaller than man size, dealing 1d6 damage with each forefoot which hits.
 
If more than two are encountered, the rest will be young from 30-60% mature. 

TITANOTHERE

Number Appearing: 1-12
Armor Class: 6
Move in Inches: 12
Hit Dice: 12
% in Lair: Nil
Type or Amount of Treasure: Nil

These "prehistoric" creatures are huge and fearless plant-eaters.  They roam in herds, and if any creature threatens them the largest males will charge.
 
They normally deal 2d6 damage on a hit, but will do double that on a charge.  In addition, any creature smaller than man-size may be trampled, suffering two additional attacks for 1d6+2 damage each.
 
If more than six are encountered, 1-4 of these will be young, from 10% to 80% grown. 

MAMMOTH 

Number Appearing: 1-12
Armor Class: 5
Move in Inches: 12
Hit Dice: 13
% in Lair: Nil
Type or Amount of Treasure: Nil
 
These massive herbivores are quite aggressive if threatened.
 
Mammoths attack with a combination of tusks, squeezing trunk, and stomping feet.  Each of these attacks deals 2d6 damage.  Although they may attack only a single foe twice per round, they may fight up to six opponents simultaneously.  Their attacks are split between opponents, so that if they are fighting six opponents they get one attack on each, and if fighting three opponents they attack each twice.
 
Their tusks are valued at 200-900 gold pieces each.

2 comments:

  1. I appreciate you sticking to the 1970s understanding of the Stegosaurus's back plates.

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    Replies
    1. Everything here is drawing from the AD&D Monster Manual, so it's all going to be based on 70s ideas about dinosaurs. It's scientifically out of date, but more evocative of the game's pulp sources.

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