Rank 5: Mortarion
The fact that Mortarion became a traitor at all is because he saw in the Emperor the same tyrant as he had encountered in his adoptive father on his home world. His hatred of power-hungry overlords eventually led him to Chaos.
Matching his homeworld, which was bathed in a toxic fog, Mortarion is now a Daemon Prince of Nurgle and thus a master of diseases – something that he and his Death Guard probably only endure because Nurgle himself obscures the whole thing.
As a follower of Nurgle, the Death Guard and their Primarch are extraordinarily resilient. Nurgle’s blessings make those who possess them nearly immortal. They are resistant to diseases that they themselves spread and are difficult to kill due to the nature of the god.
Through his resilience and strategy of war of attrition, Mortarion managed to secure victories against opponents like the Grand Master of the Grey Knights, the probably strongest order of Space Marines.
His knowledge of diseases brought him to the “Godblight,” a plague that can kill even Primarchs. With this, he infected Roboute Guilliman, who, however, survived through divine intervention and currently rules the Imperium.
Mortarion’s greatest strength is also a significant weakness in direct combat. He can endure for an extremely long time and wears down his enemies, leading to victories against Perturabo. However, generally, it is difficult to win defensively against another Primarch, as they are all endowed with considerable stamina. Eventually, a strong fighter will land a blow that ends the battle.
