They came from Outer Space (3): Space Crusade Mission 3 Counter-Attack

The 'badly wounded' Imperial Fist Commander ("Yellow Sarge") demonstrates considerable agility in out-running the little silver 'advanced cleaning droid' armed with 'advanced cleaning agents and anti-bacterial wipes' as the four inert bodies of his dead Space Marine Troopers are carried off by minions of Chaos to be recycled as new "zombified forms of unintelligent life" intent on attacking humanity (see below):

Chaos falls back into Quadrant Four daring the Red Blood Angels and Blue Ultramarines forward into a "trap" (see below):

Meanwhile the assault on Quadrant Four was highly synchronised by Red and Blue Teams, focused on taking out a batch of dangerous Necron Combat Androids, albeit not armed with "cleaning fluids" but the lesser "high energy plasma weapons"> The 'two Sarges' go hand-to-hand in a desperate struggle (see below):

An unexpected act of violence that shocked the confidence of the Space Marines in Quadrant Four as the Necron Android in hand-to-hand "self destructed" causing four points of damage to each adjacent "Sarge" leaving them critically wounded on only 1 Hit Point (see below):

"White or Yellow Sarge" (delete as appropriate) felt a surge of relief as he fell back onto the Ultra Marine perimeter line. As he was forming up with two Ultra Marine Troopers an unexpected "alien event" meant that a Genestealer appeared in their midst to cause havoc a wreck his hopes of stabilising thew situation (see below):

Two Ultra Marine Space Troopers fall to the claws of the dreaded Genestealer monster and next the clambering hoard of aliens (including dangerous cleaning droids) lead by a really deadly Necron Android (ask the Blood Angel and Ultra Marine Sergeants) surge down the corridor (see below, a pretty tight looking fix if you ask me):

Luckily all the hours Yellow/White Sarge had put into the "battle simulation Hollodeck" were paying off, as a cunning plan formed in his head. The first part of which was .. run away again as the Ultra Marine Troopers bodies were carried off by the Chaos monsters. (Ed: I can see a pattern forming here!)