Thenidiel Thranduiliel was a warrior, like her brother, father and the guards she considered friends. She was great with a bow, though not as perfect a shot as Legolas. When she was 200 years old she had started training in self defense with Tauriel, a rising soldier in the Mirkwood guard. King Thranduil had only permitted this of his only daughter after the recent sightings of spiders closer to the kingdom.

As a princess, Thenidiel had a different role. She was to stand by her father's throne as he greeted any guests or held meetings in the company of royal advisors. Or she chatted idly with guests during celebrations. At the times she wasn't at her father's side or training with Tauriel, she would be in her room with her tutors. It was a much different expectation of the royal family than the other Silvan elves of the kingdom. They had all had private studies and tutors, along with weaponry and training to hunt and fight in the guard.

By the time she was 400, she had become a warrior wearing her braids proudly. Tauriel had moved to the Captain of the guard and spent more time with King Thranduil and Legolas than Thenidiel. And at 500, Thenidiel knew she wanted more than to be stuck in the woodland kingdom.