Chantir

Biography
Chantir met the Doctor during the Last Great Time War. Chantir was taken prisoner for unknown reasons and was imprisoned in the same cell as the Doctor. With the Doctor's help Chantir escaped the prison facility and helped the Doctor recover the Key of Rassilon.

The Tenth Doctor stated that he could not remember Chantir because the De-mat Gun he used wiped most of his memories of the event, the Doctor thought he had been alone in the cell.