Tara Mishra

 was a companion of the Ninth Doctor.

Biography
She was born in Sri Lanka. (PROSE: Christmas Special)

Before joining UNIT, Tara was a nurse. (COMIC: Official Secrets)

Tara fought with UNIT against the Cybermen in Halifax, and learned that they had a weakness to gold. (COMIC: The Bidding War)

She met the Ninth Doctor, Rose and Jack in Blaise Castle. She later revealed herself to be a member of UNIT.

When Albion Defence, a competing anti-alien organization, attempted to stage a series of attacks with telepathically-created monsters to create the impression that UNIT were incompetent so that they could take over Earth's anti-alien defence for themselves, Tara sacrificed her career to protect UNIT by appearing on a talk show and claiming that she was a member of Albion Defence to expose their crimes.

Tara later sneaked aboard the Doctor's TARDIS, and greeted them. She then joined them on their next adventure. (COMIC: Official Secrets)

The Doctor concocted a plan to have himself arrested for Tara's murder. Tara herself was alive and well. Her part of the plan was to free the Doctor from his imprisonment in the Hesguard Institute. (COMIC: Sin-Eaters)

After a few adventures in the TARDIS, the crew were brought off course to the site of a chat show hosted by Slist Fayflut Marteveerthon Slitheen. (PROSE: Christmas Special)

After the Doctor defeated the Cybermen when they planned to steal his memories, Tara decided to remain behind on Nomicae to help the people affected by the attack. (COMIC: The Bidding War)

Legacy
While recounting an event in the Ninth Doctor's life to Bill Potts, the Twelfth Doctor clarified that it was "before Tara". (COMIC: The Promise)