The Legend of... the Master? (webcast)

The Legend of... the Master? was a short animated prelude to the Hearts of Darkness audio anthology, released in 2020 on Big Finish Productions' official YouTube channel.

As this was not referred to as a commercial trailer by Big Finish Productions, this story can be considered a valid source.

Publisher's summary
The story of a legend... just probably not the one you were expecting.

Plot
A firey explosion shoots across a control room of a TARDIS, while an unseen individual reads from a book about a "Time Lord, a renegade", who stole a TARDIS from his world, with ambitions to see the universe and everything creation had to offer. He knows this, revealing himself to be that man... he is the Master.

Cast

 * "War Master" - Derek Jacobi (uncredited)

Worldbuilding

 * "The Master" reiterates that people claim that in warfare there are only two options - fight or flight.
 * The book has images of various individuals, species, and locations the Master came across in his travels - Time Lords, Skaro, Chantho, an Ogron, a Sea Devil, an Ood, a Dalek, and Gallifrey - a picture of him and his TARDIS is also seen.

Continuity

 * The Doctor is currently trapped in the Master's body. (AUDIO: The Castle of Kurnos 5)