They came from Outer Space (2): Space Crusade Mission 3 Counter-Attack

The Imperial Fists engage in vicious hand-to-tentacle(?) fighting but lose a Space Marine Trooper to a "freakish act of Chaos inspired chance" as a Kroot (which I am using in place of Space Orks)  shot pieces a weak spot in the Imperially blessed armour. More as yet unidentified 'aliens' are ominously moving up in the background (see below, orange dot counters representa aliens out of "Line of Sight"):

Adopting a combative stance the Imperial Fist Commander ("The Sarge") unhesitatingly orders an immediate counter attack, straight out of the operational tactic scrolls of the Corp. Huzzah! Sadly this plays straight into the hands of the Chaos player's "swarm attack" (Ed: Will try not to gloat at this point. Sorry failed, "Gloat!") particularly as a couple of Necron Androids appeared "as if out of nowhere" to bulk up the the Chaos "umpf". Three more Space Marine Troopers fall in quick succession to the complete disbelief of "The Sarge" his squad was "gone" and the holes in his battlesuit betrayed the fact that most of his Hit Points  had too (see below):

Meanwhile, at the other end of the sector, the Blood Angels are carving a path of gore and spare robot parts as the engage in a bit of room-to-room "Space Hulk" cleaning with "Red Sarge" Power Sword in hand leading the way (see below, two Kroots [aka Orcs] and a Chaos Space Marine [aka a Tau figure] fall):

So effective is he that the Chaos Commander elects to order a tactical withdrawal, taking potshots from a distance as they retreat [Ed: Ahem, in "good chaotic order"] to the next defensive position (see below):  

Buoyed by the apparent success of the Blood Angels the Ultra Marine Commander "Blue Sarge" makes an appearance taking out another Chaos Space Marine (aka represented by another Tau figure) clearing the way for an advance on the final unexplored quadrant the aliens seem to be massing in (see below):

The Space Marines seem to be advancing in one sector (with Blue and Red Teams) but are being annihilated in another (Yellow Team). Coordination seems to be somewhat lacking, or is it inter-chapter rivalry coming to the fore!