Codex: Dark Angels (2013), p23-24 — History of the Dark Angels

101.M34 Noble Passing

While leading his Chapter to victory in the Bloodpox Campaign against the Death Guard and the Brotherhood of Plague, the twelfth Supreme Grand Master of the Dark Angels, the esteemed Armaros contracts the loathsome pox. His rapid deformation convinces the Supreme Grand Master to immediately pass the Lion Helm to his successor. To ensure the contamination does not spread, Armaros voluntarily enters the Rock's reactor chamber and is wholly consumed.

[...]

314.M36-334.M36 The Trail of Unbelief

The Dark Angels begin a two decade long campaign beset with many battles to hunt down Brother Machius, a former lieutenant of Cardinal Bucharis. Despite several ambushes set by the Night Lords Traitor Legion, the Dark Angels prevail - the Ravenwing locate Machius on the plague-ridden planet of Gronmoth, capturing him at the Battle of Black Death.

[...]

891.M39 The Lost Hope of Perdition

A Dark Angels' investigation of a space hulk newly materialised out of the Warp discovers strong elements of the renegades known as the Cleaved. The ensuing fight is won when Assault Squads, advancing behind a trio of Dreadnoughts, get close enough to set cyclonic charges in the engine rooms.