New Line Cinemas has revealed the first image of Evangeline Lilly as the elf Tauriel in The Hobbit: The Desolation of Smaug.
Peter Jackson and his co-writers invented Tauriel for The Hobbit films in an effort to expand the world of the elves of Mirkwood and add a female presence to the movie trilogy's male-dominated cast.
That has upset some purists who want Jackson to stick to the characters featured in J.R.R Tolkien's original book.
Lilly, 33, told Entertainment Weekly Tauriel is "slightly reckless and totally ruthless" and "doesn't hesitate to kill".
She is the head of the Elven Guard in Mirkwood and is rumoured to be involved in a romance with the elf Legolas, who was played by Orlando Bloom in The Lord of the Rings trilogy.
"She will definitely have a love story," Lilly told Entertainment Weekly. "I can't give away too much about it. It's not a huge focus but it is there and it is important and it does drive Tauriel and her story and her actions."
Lilly acknowledged that her character was likely to upset some Tolkien fans.
However, she said Jackson and his collaborators have proved they know how to respect the world created by the British author.
"I know beyond a shadow of a doubt that there are going to be people who will totally hate Tauriel, think that she shouldn't be in the movie, that it's a betrayal of Tolkien, and no matter what I do it won't be right," she said. "There will be everything between that and people who adore her and think it's such a fun thing to have added to the film."