Elvenking

Elvenking was a title used throughout The Hobbit for the ruler of the Woodland Realm, the country of the Silvan Elves who dwelt in the northeast of Mirkwood in the later Third Age. He is never given a name in that book, but we learn in The Lord of the Rings that he is Thranduil, the father of Legolas of the Nine Walkers.

The Elvenking had his halls underground, partly in memory (it was said) of the mighty but long-lost Menegroth of Doriath. He lived in attunement with nature, wearing a crown of flowers, or autumn berries, according to the season, and his banner was, naturally enough, green in colour. During Bilbo's journey to Erebor, his companion Dwarves were briefly held prisoner by the Elvenking, and Thranduil's people were later given custody of Gollum for a time, too (though each of these prisoners was eventually able to escape).