Wandering Pit

The Wandering Pit of Vaasa, often referred to simply as the Pit, was a mysterious entity which terrorized Vaasa in the mid-to-late 14 century DR.

Description
Under normal circumstances, the Pit was completely hidden and virtually undetectable as it could perfectly camouflage into almost any terrain, whether grassy, muddy or rocky. However, when it attacked, it opened suddenly as a wide and  deep hole filled with spikes.

It was unclear whether the Pit was a creature, some kind of animate trap, or an amalgamation of multiple things.

Behavior
The Pit would appear without warning beneath the feet of its victims, snapping open suddenly and then just as suddenly springing shut with its prey inside. It would then vanish completely.

Ecology
The Pit roved all across Vaasa, attacking unsuspecting victims everywhere from the Sunderland and the Galena Mountains in the east to the Bottomless Bogs in the west.

History
The Pit appeared in the, following the defeat of Zhengyi the Witch-King and the collapse of Castle Perilous, and many believed that it was some abomination or defense mechanism that had escaped from the Witch-King's citadel. It was known to target travelers, even snatching up a rider along with their horse. In one notable case, a party of adventurers searched desperately for the Pit after they saw it snatch one of their members, but even digging deep revealed no sign of the thing. The Pit further became a menace to the dwarves of Hillsafar Hall, who placed a 500 gold piece bounty on it.