The Ecce Bellum was a Warlord Battle Titan of the Legio Debellator that was part of an Adeptus Mechanicus strike force sent from the Forge World Agripinaa into the Eye of Terror against the forces of Chaos. Its Princeps was Demaratus.
However, Ecce Bellum was captured and corrupted to the service of Chaos. The Titan supported the Iron Warriors in their invasion of the forge world Tophet VI, joining the Chaos Space Marines in their second assault on the principal hive city. Although it was able to breach the city walls, Ecce Bellum was caught in an ambush by a Warhound Scout Titan maniple of the Legio Debellator. Despite the Warhounds landing several damaging blows on Ecce Bellum, the Warlord was able to gain the upper hand in the battle, crippling the Argentum Sororis and Ruber Captrix. In the end, however, Ruber Captrix's princeps, Roan Asander, was able to get through to Demaratus, who was able to prevent Ecce Bellum's weapons from firing for long enough for Ruber Captrix to fire its plasma blastgun through the Warlord's faceplate, destroying it.
In the wake of the destruction of Ecce Bellum, the Chaos forces were driven back and Tophet VI was secured.