Family: Dinosaurs

Huge beast, unaligned

Armor Class 13 (natural armor)
Hit Points 145 (14d12 + 56)
Speed 10 ft., swim 40 ft.

24 (+7) 10 (+0) 18 (+4) 2 (-4) 12 (+1) 7 (-2)

Senses passive Perception 11
Challenge 7 (2,900 XP)


  • Hold Breath A mosasaur can hold its breath for up to 30 minutes.


  • Bite. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 4d10+7 piercing damage. If the target is a Large or smaller creature, the mosasaur gains a bonus action to use its Swallow attack against the target.
  • Swallow. Melee Weapon Attack: special, reach 0 ft., one Large or smaller creature hit by the mosasaur’s bite. The target must make a Str save (DC 18) or be swallowed by the mosasaur. A swallowed creature is blinded and restrained, and takes 4d6 acid damage at the start of each of its turns. It has total cover from attacks outside the mosasaur. If a mosasaur takes damage from a swallowed creature, it must make a Con save (DC equal to damage dealt) or regurgitate all creatures in its stomach. If the mosasaur dies, a swallowed creature can escape by using an action to crawl 10 feet back up its throat.


Inland seas are home to a variety of large, hungry marine predators, but none are feared as much as the terrible mosasaur. A throwback to a far-distant past when giant reptiles roamed all the oceans of the world, the mosasaur is thankfully rare in the present age. They have been known to sink galleys by ramming them beneath the waterline, then gorge themselves on a dozen or more of the surviving sailors as they struggle in the water. Mosasaurs have also been known to crawl ashore and attack coastal villages, although they are slow and clumsy on land.

Stocky and powerfully built, this great cat’s most salient feature is a pair of foot-long fangs jutting down from its upper jaw.

Section 15: Copyright Notice

Primeval Thule Campaign Setting Copyright 2021 Sasquatch Game Studio, LLC. Design Richard Baker, David Noonan, Stephen Schubert

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