This is AU Dark Thranduil, many centuries after events of The Hobbit and The Lord of the Rings. Inspired by Mandragora Scream song.
Most elves left to West, but Thranduil stayed 'till Erebor stands'.Centuries and millenia go on, and Erebor still stands. Even dwarves have left long time ago, but Erebor still stands. It is covered in woods now, and in those woods Thranduil lives. As all others who stayed, he became the spirit over time, and appears in visible form only on most rare occasions. From loneliness and desperation he went mad and now he exist for sole purpose - to protect the peace of the woods and the mountain, and his great love, buried under the mountain.
Now only humans live around, and they have legends about great treasures of the woods and mountain, and from time to time some brave fellows - alone or in groups - go and try their fortune there. And usually that's the end of them. Some fall into swamp, others get crushed by fallen tree, and so on. Many bad things can happen in the forest.
Also rare survivors sometimes tell stories of the creature of unearthly beauty, with shining eyes and green clothing, in crown of flowers and berries who comes to the fireplaces of treasure hunters and proposes the toast to welcome company, and everyone drinks, mesmerized. And those who get to taste the drink will fall asleep and will never awake. Survivors are those who realized what is going on in time and started running as soon as their comrades started falling. And they said that when they were walking into the forest, the path was elusive and difficult to find, but when they were running away, the path appeared on its own under their feet...