Tecteun (Once, Upon Time)

An incarnation of Tecteun who also used the name "Awsok" survived the destruction of Gallifrey by, having been on the Division's space station in the Void between universes at the time. (TV: Survivors of the Flux) She appeared to the Thirteenth Doctor right after the Doctor left her friends' time streams.

Biography (as "Awsok")
Awsok knew the Doctor, and appeared to have vast knowledge and power. Unlike other individuals the Doctor encountered while traversing her time stream, bar perhaps the Fugitive Doctor, Awsok was aware of the Thirteenth Doctor's presence and physical location on the planet Time.

Awsok considered the Ravagers, Swarm and Azure, to be "rare and useful creatures"; and informed the Doctor that they had been "reintroduced" as a "temporal poison". She also knew of the Flux: that it wasn't a natural event, but rather was made; "It was placed".

Awsok informed the Doctor that she (the Doctor) was fighting a lost cause, that the universe was over, and that it was all the Doctor's fault. With that, she advised the Doctor not to come looking for her and told her she could go. The Doctor reawoke in the Temple of Atropos. (TV: Once, Upon Time)

Behind the scenes

 * The name "Awsok" was not used by any characters, neither in Once, Upon Time or Survivors of the Flux. Instead, the alias originated from the credits of Once, Upon Time, to conceal her true identity.
 * It is unclear as to whether "Awsok" is the third incarnation of Tectuen, or merely the third covered by the series.