Ah'len was a Xyrillian engineer who came from the city of Thera. Her favorite food was dutara root.

In 2151, Ah'len assisted Charles Tucker III in repairing the engines on her ship. She had a brief flirtation with Tucker. After the ship was repaired, Ah'len showed him Xyrillian holographic technology, recreating two different landscapes from her homeworld. While sitting in a holographic boat in an ocean, she and Tucker immersed their hands into a box of granules which began to glow, enabling them to read each other's minds, and transferring energy between the two. As it also transferred genetic information, this interaction with Ah'len caused Tucker to become pregnant.

Tucker did not realize he was pregnant until he left Ah'len's ship, although he knew they were attracted to each other. It was the first documented occurrence of a Human male becoming pregnant. After Enterprise NX-01 tracked down the Xyrillian ship, Ah'len became aware of the pregnancy, but was surprised that fertilization could occur with another species. She scanned the embryo and determined that it was a female. It was safely transferred to another Xyrillian host. (ENT: "Unexpected")

In the script of "Unexpected", Ah'len is introduced with the description, "She's curiously attractive in a bizarre sort of way."
Ah'len was played by actress Julianne Christie. The costume worn by Christie as Ah'len was sold off on the It's A Wrap! sale and auction on eBay. [1]