Bore worm

The bore worm was a massive, unique construct created by the "Metal Mage" Trobriand, designed to resemble the subterranean purple worms of Toril. It was in effect an enormous digging machine that dwelled within the dungeon-complex known as Undermountain.

Description
Beyond massive in size, the bore worm was even larger than the purple worms after which it was designed. It was made of metal, the exact type of which was unknown, and had enormous grinding jaws positioned in the front of its "head".

Due to its size and construction, the worm was immune to poison and could not be blinded, deafened, immobilized, petrified or affected by any form of psychic magic or energy. Its metal form was extremely resilient and could only be damaged by weapons made from the metallic alloy adamantine.

Behavior
First and foremost, the bore worm obeyed any direct orders issued by its creator Trobriand. If it was free from any direct commands, the worm tirelessly writhed through a series of often-used tunnels it had excavated throughout Undermountain.

History
Sometime prior to the Year of Three Ships Sailing, 1492 DR, the bore worm dug out a vast network of tunnels that connected Trobriand's Graveyard with the Maze Level above along with Arcturiadoom below.