The De Profundis was a Battle Barge in the Word Bearers Legion's Serrated Sun Chapter[1a] and also served as the Flagship of the 1,301st Expeditionary Fleet during the Great Crusade[1c]. It was commanded by the Serrated Sun's Chapter Master Deumos[1a], until he was killed by the Adeptus Custodes Vendatha during the Primarch Lorgar's Pilgrimage[1b]. Afterwards, it was commanded by Chapter Master Argel Tal and later took part in the Dropsite Massacre; where it fired upon the unsuspecting loyalists.[1d]
Later in the Heresy, the vessel fell under the control of the Possessed Word Bearer Toc Derenoth who fused with its Machine Spirit to create a semi-sentient Daemonic monstrosity. At the Battle of Anuari the De Profundis led a traitor ambush against Roboute Guilliman's fleet and Toc Derenoth intentionally destroyed the vessel in order to bombard Guilliman's ship, the Samothrace, with debris in order to lower its Void Shields.
- 1: The First Heretic (Novel)
- 2: Ruinstorm (Novel) — Chapters 1–4