Behemoth

Behemoths are the biggest of the saurians and among the most terrifying monsters of the Antediluvian Age. Luckily they are rare and spend most of their lives asleep underground. They reach up to two hundred feet (the appendix gives 100-140 feet), armored in horny scales said to be as tough as plate mail. Like most reptiles they have a slow metabolism and move sluggishly, and they cannot survive cold, living only in subtropical, tropical and desert lands. Sightings are so rare that their breeding is a mystery.

A behemoth can hibernate for up to seventy years without stirring unless something disturbs it, in a burrow 30-60 feet deep and as much as a mile long. On waking it crawls out and spends seven days roaming and eating every bit of organic matter it finds, covering up to seven miles a day and leaving a trail of wreckage a hundred feet wide. In this frenzy it is fearless and savage; tales tell of them charging armed crowds and smashing farms and walled cities. Its claws can crush a warhorse and it can swallow a grown man whole. Loud noise, a sudden rise in temperature close by, or digging underground within 500 feet can wake a sleeping behemoth. It swallows a human-sized foe whole on a roll of 20, and cold deals it half again as much damage.

For all its power it is extremely stupid. It cannot understand even the simplest command, which makes it wholly immune to magical influence, and it is driven only by the instinct to eat whatever looks edible. When the frenzy ends it digs in again for another long sleep. Behemoths are thought to be close to extinction, and their random wanderings seldom strike civilized lands, yet towns, cities and forts have sometimes been built unknowingly on top of a sleeping one.