"The Conquistador" was the self-styled title of a young homeworlder who was trained for combat in the War in Heaven. During their training they were told that one potential identity of the Enemy was Tardigrades. (PROSE: The Short Briefing Sergeant's Tale)
When giving example of the sort of titles Time Lords used, the Fifteenth Doctor mentioned "the Conquistador" as an example. (TV: Space Babies [+]Russell T Davies, Doctor Who series 14 (BBC One and Disney+, 2024).)