Codex Adeptus Astartes: Grey Knights (2017), p26-27 — Lord Kaldor Draigo

So it was that Kaldor Draigo, Lord of the Grey Knights, came once again to Acralem. He spoke few words, yet his grim purpose was plain to behold as he trod old battlefields reawakened to fresh slaughter. At the siege of Castle Gorseth it was Draigo who unleashed the psyflame that swept the Daemons away, and he who struck down the plague-rotten abomination that commanded the assault.

[...]

He became Supreme Grand Master in late M41, following the slaughter of the previous Chapter Lord at the hands of the Daemon Primarch Mortarion, and in the same battle he carved his forebear's name upon Mortarion's rotting heart - an insult that the Daemon has never forgotten.

[...]

For an uncounted age Draigo wandered that terrible, ever-shifting landscape. His path was strewn by Daemons who sought to slay him or seduce him to darkness, yet through bitter struggle Draigo overcame each of them. [...] He unleashed sanctified flame again amongst the writhing jungles of Nurgle's domain, and for a long time the gusting warp-winds that buffeted him carried a charcoal stench and the tortured screaming of daemonic vegetation.

[...]

Chief amongst his quarries is his enemy of old - the Daemon Primarch Mortarion, the murderer of his predecessor.