Long before the destruction of Tanith and the rise of its Ghosts, Commissar Ibram Gaunt serves with the Hyrkan regiments on the front lines of the newly-launched Sabbat Worlds Crusade. Descending beneath Sangrel Hive in search of an ancient shrine to Saint Sabbat herself, Gaunt and his men encounter something altogether more sinister.
Although published in 2013, this short story is chronologically the earliest and depicts Gaunt as a younger officer before he formed the Tanith.
A Gaunt's Ghosts short story by Dan Abnett.
