Critical Threat - Khan the Betrayer

Khan was identified by savants of the Ordos Dintera Minor from witness statements of the Umbrella Factory attack

Khan led over twenty adherents of Khorne (cf "Khornate Berserkers") into the resting 1st battalion of the 1293 Hrossy Yeomanry as they pushed into the north eastern quadrant of Xyphonica.

The Chaos space marines, optimised for close combat, were able to cause a disproportionately high number of casualties before being fought off, meaning that the Hrossey Yeomen were then unable to hold their position and had to rolled out of the front line for a considerable time.

And multiple close and point blank hits by hand held plasma weapons immobilised a lot of the chimera fleet that were lagered in the factory complex.  

Paint by Colonel Scipio.