So I'm playing a duet game with my bud who's playing a black templar assault marine while I NPC a Devestator (there aren't many RPers where I live). The mission was to assassinate a planetary governor (who artificially ascended to daemonhood and warped the entire capital to Chaos after one of his cold-trade halo artifacts backfired on him) and retrieve the xenos artifact in question. The mission was set amidst a backdrop where 1.5million imperial troops and armor were laying seige to the hive capital with brutal trench-warfare tactics against the entire 40 million+ warped population, and orbital assaults were rendered ineffective due to a fully functional orbital defense grid.
Primary Objective: Neutralize the source of the moral contaminant and retrieve the halo artifact.
Secondary Objective: Neutralize any military assets critical to the Enemy's infrastructure.
Tertiary Objective: Neutralize any targets of opportunity.
Long story short, my player contacted the Guard general from orbit for up to date intel (countering my pre-rolled mishap of incorrect battlefield intelligence. Bravo!) and ACTUALLY convinced him (under the false pretense that they were an entire Astartes company here to aid them) to divert all forces and to charge the enemy's southern defense line as a diversion while dangerously exposing the Guard's northern flank. This allowed our characters to deep strike in safely under the enemy's nose and out of range of the orbital defense grid to advance on foot to the corrupted hive. Sadly, the General never received his reinforcements and the entire northern flank was swept under a tide of bloodthirsty cultists and the guard defeated in a matter of hours. The General called down an orbital strike at ground zero in a final act of suicide, turning the battle zone (miles away from the characters) into a hellish landscape of atomic fire and burning winds.
The characters found and eliminated the source of the enemy's unending supply of troops: A corrupted manufactorum which held a foul portal open to the warp and sustained by a coven of rogue psykers. My devestator slew the wych horde with a belt full of krak grenades, interrupting the ritual and imploding the entire structure ( inadvertantly angering the patron greater daemon aiding the wyches). The massive beast emerged from the portal and marched outside on a killing spree slaying any cultists fleeing the area while the characters sneaked into the hive via an abandoned monorail structure.
After sneaking to the top of the highest spires piercing the blood-red stormclouds covering the landscape, the players entered the governor's corrupted sanctum sanctorum: A massive, vaulted volume of space many kilometers in diameter contradicting the laws of spatial dimensions.
Now I've known my friend for many years and I've never seen a look of horror on his face like I did last night.
The room was jam-packed wall to wall with hundreds of thousands of gibbering cultists and suspended in the middle of the foggy volume was a blinding red light. At first my buddy believed them all to be just a giant horde and used his jump pack to speed over their heads gallantly towards the red light in the center (while my character was still stuck climbing up the elevator shaft....). He valliantly dodged lasfire and dropped a few frags into the hordes, but he noticed the massed bodies began to meld together the closer he got to the center. When he saw the gigantic, shining serpentine form of the governor held aloft by a 300 meter tall pillar of screaming intertwined bodies of cultists for a tail, my friend failed his willpower test and crashed into the mass of bodies making up the beasts skin (all reaching up to pull him under).
Massive tentacles of flesh erupted out of the mass and swung at my player and though he dodged many attacks and inflicted many blows with his thunder hammer, he failed to cause any more than superficial damage to the fleshly pillar suspending the Daemon well out of reach. He was reduced to 7 wounds from an ill-dodged hit. My character finally climbed to the top floor and imploded the beasts suspension with a well placed lascannon shot tipping it over. The shock ripples sent my friend flying a safe distance away from the beast while my character dropped the cannon and unleashed a hail of heavy bolter fire chewing away at the beast. My friend charged the monster which stood easily five times his height and delivered a flurry of blows (only causing superficial damage). In the end, it was the bolter which held the victory. The artifact was retrieved by my battered friend and they managed to escape before the hive collapsed (bereft of the warp energies that held it together).
This was a 2-day adventure so I awarded my friend 5 renown and 1000exp. for completed objectives and playtime. He really had some fun with this adventure and it afforded the player the opportunity to affect actions occurring in the background. A straightforward "run and gun."