Straxus used a Time Ring to find the Eighth Doctor during the Morbius incident. Lucie Miller stole it from him. (AUDIO: Sisters of the Flame)
The Doctor then tried to use this time ring to escape the Sisterhood of Karn's dispersal chamber. (AUDIO: The Vengeance of Morbius)
During the War in Heaven, Straxus' Time Ring malfunctioned while he was in 1888 Ceylon, stranding him and a Cwej. The Ring still had spatial transportation capabilities and Straxus used it to enter sealed Egyptian and South American tombs and collect artefacts to auction with Straxus Imperial. In 1893, an emergency setting of the Ring overrode Bernice Summerfield's Time Ring and brought her to London. (AUDIO: The Adventure of the Diogenes Damsel)
He later used another one to travel to the Doctor's TARDIS as the Doctor tried to travel to the end of the universe. (AUDIO: The Great War)