Codex Adeptus Astartes: Grey Knights (2017), p25 — M41 Age of Maledictum

Plagues of Ultramar

The Exactors send Strike Force Cautery to Ultramar to aid the Ultramarines and the Ordo Sepulturum in the fight against the Death Guard, who are spreading daemonic plagues across the region. With knowledge of the Heretic Astartes' viral proclivities gleaned from the tomes in the Sanctum Sanctorum, the Grey Knights are able to cripple two vectoriums of the Death Guard's 4th Company and eradicate the Consumptiphagus strain of the Eater Plague.

The Putrid Springs

The 2nd Company of the Scythes of the Emperor, newly reinforced with Primaris battle-brothers, finds itself under siege upon the hive world of Hamagora, assailed by an endless swarm of Nurgle Daemons. Intercessor Squads establish a punishing series of kill-zones amongst the ruins of hive city Agrippa, yet for every Daemon they slay, two more emerge from the dank tunnels of the undercity, and their casualties begin to mount. Operating in total secrecy, Strike Force Harbinger of the 5th Brotherhood teleports into the sub-city. Their quarry is the Great Unclean One Gul'gulm'ga'tol, who has turned Agrippa's sprawling sewage works into his personal baths - hordes of putrid Daemons crawl endlessly forth from the morass of rancid gruel. After a bloody battle, the strike team sends Gul'gulm'ga'tol screaming into the warp. Hamagora is saved, though the Scythes never discover how.

[...]

Draigo and Mortarion

With the Great Rift yawning open and pouring all manner of Chaos monstrosities into realspace, Lord Kaldor Draigo, Supreme Grand Master of the Grey Knights, finds he is able to escape his imprisonment in the warp more frequently and for greater lengths of time. Draigo materialises to aid his battle-brothers in multiple war zones across the Imperium, often turning grim defeat into a decisive victory for the Chapter. Though he quickly fades after each encounter, he imparts to the Grey Knights with whom he fights visions of things to come that he has witnessed within the immaterium. Many of the Prognosticars, seeing the strands of ancient hatred that bind the two together, believe that Draigo's presence is inextricably linked to that of the Daemon Primarch Mortarion.