Amidst the din of chaos consuming the moons of Phalanx, A distress call is heard from one of the larger moons. Kraxxus is under siege! Though the message is difficult to make out, it appears that the mining operation on Kraxxus has uncovered some strange xenos archeotech that has reactivated itself and is potentially sending its own distress beacon.
Not far away in Erinyes Nebula, alien eyes descend upon the source of the beacon, soon thereafter followed by the silent wake of their sleek starships.
Just as the attacking forces start to arrive at the battlefield, the defenders erect a forcefield cutting off a portion of the attacking forces. Likewise, the defender has dedicated a portion of their force to facilitate evacuation while the rest remain behind to buy them time and recover the archeotech data.

I was chomping to play some big bad bugs this week, so our warmaster did the traditional move in a narrative setting - generate a contrivance that allows all the factions in 40k to show up.  It ain't hard mind you, but it's always silly when you try to justify why everybody is there ready to throw down.  We have tyranid bio-research labs, a necron tomb world, the Eldar show up just because - well, hopefully, the Eldar fuck off for the whole season.  Orks will, I suppose, just Ork on over because we're brawling.
We have a club Tyranid army that was thankfully left by a friend of ours after the warp storm table destroyed his desire to play forever.  Seriously - two games, two first turn 11's, two failed leadership tests.  First blood, slay the warlord, 300 points gone.  But the legacy remains.  Because I ruined his game, I'll at least use his miniatures.
My List for the Week (unbound):

Endless Swarm
3x 18x Hormagaunts, Adrenal Glands, Toxin Sacs
2x 17x Termagaunts, Fleshborer
3x Warriors, Devourers

Swarmlord
4x Hive Guard, Impact Cannons
2x Trygon Prime
2x 3x Venomthrope Brood

The twist this game is that there is an attacker and a defender.  The attacker has 500 points extra, but has to destroy the force field objective or his units entering from reserve die on a 1-3.  The defender scores secondary points from holding objectives, the attacker from destroying them.  It actually seemed pretty fair, and we had some good games.  I wiffed my second because I thought I didn't get my extra 500 until I took down the force field, and I kept killing hormagaunts on the field, and the primary is purge the alien.  I took the first through ballsy reserve antics, eventually tabling my opponent despite the force field taking me down more than 500 points.  Give it a try, it was fun:
https://drive.google.com/file/d/0B2FffKNu2uAEXzd0X2s0cHVwWnM/view?usp=sharing
My list in the first game involved a flyrant w/ 2x devourer w/ brainleech worms.  I had to take him out for the second game, and he won't be returning in this season.  They're just too meta to take in a friendly game session.  I should give anyone who brings really meta stuff a hard time - though I don't know what those are, and everybody is bringing fun stuff so far.  Our IG player brought chimera rush/russ wall, which was awesome to see.  He's been spamming WKs and WSs for so long it was a pleasure to see his first love on the table.

Funny story, actually, he was able to field that much armor because he raped a friend out of the game quite a while ago.  First time playing IG against Wraith Knights, Dawson decided that the game was bullshit and he wanted out.  So Hagen bought him out for cents on the dollar, he turned that money into some orks that were lying around the garage, and two tables held the legacy of unfair codex creep today, with the rapists gleefully playing with their unfairly begotten gains.  Friendly games built upon a legacy of pain.  You just can't escape the grimdark.
So Tyranids beat Minotaurs, Astra Militarum beat Blood Angels, Sons of Medusa beat Tyranids, Blood Angels beat Tau.  Hopefully next week we'll upgrade to triple table, this season is generating a lot more interest since everyone has more of a fighting chance and we can bring all our cool stuff.
***
It seemed as though Kraxxus itself was in pain.  From all directions the wail of alarm klaxons and air raid sirens sounded.  Every mechanical mouth upon the innumerable bastions across the surface screaming.  The residents of the moon are woken by the sound from unquiet dreams into a true nightmare. 
PDF soldiers run everywhere, identifying key personnel and hustling them towards waiting ships.  Those who can be easily replaced are formed into hurried conscript squads, given antique lasguns, and told to hold for reinforcements.  The Emperor does not lie, but his servants may.
The planet is lost, the traitor is landed, the xenos is come.  It is possible to escape this terror, but the galaxy is rent by war.  There is always another terror, for they lurk between the stars.
Eyes craned towards the sky, the bronze-armored Minotaurs man their AA guns and wait.  But the terror comes from beneath, the scythe-mawed worms erupting from beneath them, innumerable ravenous bodies spilling from the wound in the soil of Kraxxus.  The wrath of bolter-shell can hold them back, but eventually the clips run dry, and the stream of flesh from the burrow-holes is ceaseless.  All who fought that day are lost, their precious gene-seed turned into food for the xenos.
Upon the same battlefield not hours later, the husk-armor of the minotaurs is found by a Blood Angels strike force.  Driven into rage, they hurl themselves against the nearest foes, the last armored column of the PDF upon the moon.  Their wrath is ill spent, for as they fly towards those metal walls, they are cut down to a man.
The Sons of Medusa come then, hungry for vengeance, two of their ancient dead walking with them, a column of Astartes armor backing them.  They meet the xenos with a wrath worthy of a Primarch, denying their advance again and again.  The great machine-affinity they hold modulates the force field so it hums with the twisted life-force of the xenos, making their tiny brains burst as they trample forward.
This world was already lost, let the records show.  For the blue-skinned xenos had established themselves and their insidious creed upon Kraxxus.  The people's minds were poisoned already.  Let none remain.  The Blood Angels, limping from their defeat at the hands of the PDF, fall upon the Tau with a fury that leaves none alive.
The world burns, but there are none present to exact exterminates.  The Astartes ships destroy what they can from orbit, some of the pulsing hive-mounds shattered in pulpy showers of chitin and blood.  But they will rebuild.  The last flashes of resistance are soon extinguished; Kraxxus is lost.