Mortarion's experience wasn't unique. The revived Blackwatch weren't powerful—not even as strong as an ordinary Greater Daemon. Even Guilliman could smash these Aberration mongrels with a single punch.
But the defenders soon discovered that with every death, the Aberrations known as the Blackwatch became impossible to kill. As long as even a scrap remained, they would always revive in an even stronger form.
Even when facing formidable opponents like the Primarchs, the damned Blackwatch would fuse together, making up for quality with quantity.
They were like cancer cells. Leave them alone and you'd die; attack them and they'd spread.
Mortarion encountered Ross. After killing him for the eleventh time, the Aberration that had once been easy to dispatch with a single blow had changed beyond recognition. Four phosphor wings identical to Mortarion's had grown from Ross's back, and his body had transformed into a twisted moth made up of nothing but metal scrap and fleshy tendrils.
The good news was that the pair of Blackwatch who had been surrounding Mortarion were gone. The bad news was that they had all fused into Ross.
Mortarion's painstakingly maintained armor shattered with a shriek. His phosphor wings were corroded by living acid, pocked with honeycomb holes. The broken bones in his arm pierced his armor, and yellow-green pus dripped down the grooves of his scythe, scorching the scorched earth and sending up wisps of toxic smoke.
When he cut Ross's head off for the eleventh time, the Aberration spewed not blood, but writhing clusters of neural synapses. They convulsed wildly in the vacuum, wrapped in metal fragments as they rebuilt their bodies. Mortarion had no choice but to make a tactical retreat.
As he retreated, he caught sight of his other brothers.
Sanguinius, blessed by the Chaos Gods, had three of his golden