Black Guardian - list of appearances

Season 16

 * The Armageddon Factor - (introduction)

Season 18

 * Logopolis - (flashback; archival footage)

Season 20

 * Mawdryn Undead
 * Terminus
 * Enlightenment

Doctor Who Magazine

 * Time & Time Again

Virgin Missing Adventures

 * The Well-Mannered War

Big Finish Doctor Who Audio Dramas

 * The Key 2 Time - The Judgement of Isskar
 * The Key 2 Time - The Chaos Pool