Lhachglín

At the source of the Enchanted River of Mirkwood, there lies a tower. Sarn Goriwing, the Wood Elves call it, and though it lies close to their realm, they dare not approach. There is a power there, and the power corrupts the river. The tower is the home of Lachglin the Loremaster, one of the Dark Lord's minions.

Lachglin was once accounted amongst the wise, a Dunadan Loremaster of Arthedain, a student of the Seers of Fornost. But like many others who studied the arts of far seeing and magic, he was tempted by the darkness. Lachglin fell into the Witch King's snares, and for decades he was the Witch King's spy in Fornost Erain. His treachery was discovered, but Lachglin fled with his life. From Angmar, he was sent to Dol Guldur. At the feet of the Necromancer, he learned the arts of sorcery and enchantment. He was an apt pupil. Proving himself, he was given the task of claiming Sarn Goriwing. There was an old power there, and he set about calling it forth again.

The Dark Lord gave his minion one more gift, the  Dindair demon,  the Silent Shadow .

The Enchanted River flowed dark again, thick with bewitchment and dreams.

Lachglin the Animist remained at Sarn Goriwing for the remainder of the Third Age. He was a power of the darkness set against the realm of Thranduil for a thousand years. Lachlin's sorcery and his bound demon and the power of the Enchanted River kept Lachglin ageless. Lachlin was driven out of Sarn Goriwing early in the 4th Age, though he himself remained a threat for long years of men after.