According to Ultramarines legend, the Rock was where Roboute Guilliman beheaded the rebellious Consul Gallan, who had murdered his co-Consul Konor, Roboute's adoptive father. The Ultramarines themselves use the Rock as a place of execution, for members of the chapter who have been condemned for serious crimes.
Gallan's Rock is strongly similar to the Tarpeian Rock, located in Ancient Rome, a traditional place of execution for Romans convicted of treason against the state.
- 1: Consequences (Short Story) by Graham McNeill
- 2: Dead Sky, Black Sun (Novel) by Graham McNeill, Chapter One