Arachni

The Arachni were a race of spider-like creatures who dwelled on Middle-Earth around the age of Mythos. They formerly controlled a large portion of territory around the West Bank, were not heard of after the Arachni-Troll wars.

Genesis
After the collapse of the Black Empire during the Sin War, the trolls formed Middle-Earth's first great empires, and there was little serious challenge to their hegemony until around -17,000. Agony ascended to the throne, and set her jealous eyes on the imposing citadels and impregnable walls the trolls built to protect their cities. Her heart swelled with envy when she realised just how powerful they had become, and decided that someone had to stop their advance before they became a second Black Empire, just under different colours.

Calling on her finest warriors, Queen Agony assembled a great Arachni army that would do battle against the trolls, shattering their fortresses and bringing down their strongholds. The aim was to destroy the most powerful pockets of troll power and weaken their central power to the point where the Arachni could knock them out in a single assault. So begun the Arachni-Troll wars, a battle between two expansionist civilisations.

Arachni-Troll Wars (-17,000)
The offensive against the forest trolls was underway. Queen Agony entrusted her greatest general, Tarantulon the Warmaker, with leading the armies of the Arachni into battle. She made him promise not to fail - and never did he do so. Battle after battle, Tarantulon defeated the trolls, and his onslaught seemed unstoppable. Even in the wake of impossible odds, the Warmaker seemed unfazed, and built the Arachni an empire of their own to rival the trolls. Given that each race of troll (desert, dark, forest, ice etc) were trying to defend their own domains, everyone pretty much let the forest trolls suffer.

King Florus, leader of the forest trolls, decided he had had enough of Tarantulon and his piratical streak, and devised a plan to get rid of him. He lured the Arachni into Everwood Forest, then launched a surprise attack from under the cover of the canopy. It failed. Their adversary was prepared and the Arachni struck back, routing the forest trolls. They suffered heavy casualties under the ambush, but survived to tell the tale - expect Tarantulon, who disappeared at some point during the fight. His body was never found, nor was any trace of the Warmaker discovered in the ensuing days.

Devastated, Queen Agony expended obscene amounts of resoures trying to find him, to no avail.

The Arachni became irrelevant after the disappearance of Tarantulon, and the trolls rose to power again, not to be competed with until the rise of the sarmatians in -11,000.