The former 'Lost' actress has signed on to play a new character, Tauriel, but director Sir Peter Jackson refused to give any further details about the woodland elf.
The filmmaker revealed on his Facebook page: "Her name means 'daughter of Mirkwood' and, beyond that, we must leave you guessing! (No, there is no romantic connection to Legolas.)"
Also joining the cast for the start of the second block of shooting is Australian actor Barry Humphrie s- best known for his female comedic alter ego Dame Edna Everage – who will portray the Goblin King, with extensive use of motion capture technology.
Peter said: "We're looking forward to seeing him invest the Goblin King with the delicate sensitivity and emotional depth this character deserves."
Last week, it was announced Luke Evans and Benedict Cumberbatch had joined the cast of the two movies, playing Bard and Smaug respectively.
'The Hobbit: An Unexpected Journey' and 'The Hobbit: There and Back Again' will be released in 2012 and 2013 respectively. Both releases will star Martin Freeman as the titular character.
