Klingon War Timeline[]
In an alternate timeline that was created when the USS Enterprise-C disappeared during the Battle of Narendra III, the Klingon Empire was at war with the Federation in 2366.
In this timeline, Natasha Yar (who went by Tasha) was still alive in 2366 and serving as the chief of security on the USS Enterprise-D.
She formed a romantic attachment to the Enterprise-C's helmsman Richard Castillo while helping repair the Enterprise-C when it emerged from ta time rift into 2366.
When she learned from Guinan that she was apparently dead in the "correct" timeline that would hopefully be restored by the return of the Enterprise-C to its time, she requested a transfer to that ship to help in its final battle so that her death would have meaning. (TNG: "Yesterday's Enterprise")
She would survive the battle of Narendra III and be one of the crew of the Enterprise-C taken prisoner. A Romulan leader would take a liking to her and convince her to become his wife in exchange for the lives of the rest of the prisoners. During this time she became the mother of Sela, a half-Romulan/half-human hybrid. She allegedly dies at some point during an escape attempt while Sela was young.
On the Pod[]
This version of Tasha is discussed on Stardate: Supplemental in episode 31 "Radio Letters". Her presence in the Viggo timeline is not directly mentioned, however, due to a different ship being involved in the What Would DeSoto Do segment.