(General POV)
Location the Hiveworld Kolbaline, Capital Hivecity, Atlas Primoria-Three months ago...
Nidhog was charging its attack, sparks of violet, and black lighting surging through the outer mouth of the pale grey skinned giant monstrosity.
The CO within the highest level station was demanding that the weapons be ready and online immediately, but one of those operating the system through a green holoscreen panel regrettably informed him that the crew in charge of loading the main cannons, guns, and other weapons are unable to do as commanded because majority of their crewmen have fled, meaning they have no weapons at all to attack the monster, enraged the CO slammed his fist onto a frame of the main holo system at the center of the deem chamber slightly illuminated by the various green colored holoscreens and panels around the chamber, as the CO looked as the main holo watching as the monster continued to charge up it attack, now it's outer mouth was slightly open with more electricity surging and gathering in the thirteen points as the power was channeled, gathered, and form into a miniscule violet and black colored sphere, very slowly growing in size and obviously in power as well.
As their time was growing shorter, the more time they waste the CO, then he gave his order to focus all remaining power into the shield, if they can't attack, then they can at least defend themselves hearing this command the operators and other officers within the control station tried once again to make their CO to reconsider and order a retreat which only infuriated the man as he yelled "Silence!!! Atlas Primoria is our beacon and final bastion against these blasted traitors and their scum!!! And...you...cowards!!!! Dare suggest that we allow the enemy to destroy it!!!!?" his proclamation shocked everyone as he reached inside his coat's right inner pocket and pulled out a bolter pistol, and shot six random people in the room as smoke escape the hot barrel of the gun he spoke in a voice filled with authority and promises brutality for those that didn't obey "This is my order. Focus all power on the force shield, we will protect our capital with our lives... Guard!!!" as he said the last word, the guardsmen immediately stood before him and saluted as he ordered them to quickly head to the other stations and weapon chambers once they survive the incoming attack they'll once again attack the monster.
The CO, he dismissed the guardsmen, but just before they left out the door, he gave his final commands to execute all those disobeyed orders and those that try to run, knowing the CO was serious and afraid for their own lives they simply responded with "Sir!" and left just as they were commanded to do.
All the while, Nidhog continued to charge up it attack moments later under threat and high command the guardsmen re-engage firing once again at the Titan Chaos Spawn, but like before all damage even from tanks and heavy bolters were nates buzzing around Nidhog only as a nuisance for the super chaos mutant beast that even now it still mutating by the ruinous power of Chaos.
The Kolbaline Guard desperately trying to stop Nidhog, but none of their weapons have enough power or are blessed by any sort of deity, or do they possess the strength of will and conviction to harm the titanic spawn.
As people tried to escape, they were only gunned down by the guardsmen stationed at the edges of Atlas Primoria, under strict orders of their commanding officers, they were also forced to shoot not only defenseless civilians of various age, but also some of their brothers and sisters within the Guard that also tried to escape the capital.
So, as a final act of desperation, some of the guardsmen using Sentinels run off the edge of the highest to jump onto the monster and use grenades and other explosives to bring the monster down, many performed the jump with few managing to land on the creature, and immediately rushing towards its head and in turn its ever slowly opening outer mouth that is already allowing people to see within the reddish shade of the inner mouth, and the rows of razor-sharp curved teeth but what was more frightening was the energy it was gathering was staring to further affect the ambient around.
The ground that was now being struck by volts of strong violet, black, and now purple colored lighting wasn't only being damaged and burned but also mutated, turning corrupted in stains of violet and maroon, as wrighting with dark biomass spreading across the area only stopping when in contact with the force shield surrounding the hivecity, Atlas Primoria that the ground was hissing and screeching in pain as it burned, and also the skies as the cloud continue part and being forces away, from normal colors of the mid-day sky started to gain tints of violet, maroon, and black in a swirling pattern almost reacting to the power that Nidhog was still gathering even the three colored sparks of electrical energy from it body were wildly surging upwards to the skies as well.
Seeing this, the few surviving guardsmen that managed to land upon Nidhog bravely charged forward to their target in hopes to finally bring down the pale skinned atrocity.
Running across the back of Nidhog when a guardswoman was suddenly impaled by a wine colored tentacle that just sprouted in the back of the monster, as she spat out blood and reached down at the tentacle that was impaling her belly, said tentacle started coiling around her tightening knowing she was about to die she weakly reach for one of the explosives she was carrying and weakly said to her fellow Guard as they looked at each other "Run..." as she activated the explosive as finished saying "For Kolbaline...!" seeing her do this, the other ran from her position as fast, and far they could when a huge explosion was heard from behind them, this of course wounded Nidhog making it hiss but not stop charging it attack but this also meant it knows that their on it back now.
The guardsmen rushed towards the head of Nidhog when multiple tentacles sprouted from the monster's back, swaying and wiggling frantically as they all struck at them, trying to either grab or impale them when they tried to simply shot at these tentacles, the results were that for every tentacle that they blasted or cut it would regenerate and attack so their only option was to run through them, and dodge their attack.
But the multitude of tentacles and the speed that they sprout in random spots has made this last attempt to stop Nidhog much more dangerous, as the tentacles continued attacking the guardsmen, and one by one the wine colored tentacles managed to capture or kill their prey, those that still have some life in their bodies did as their fellow guardsman and triggered thie explosives to take out as many tentacles, and provide a chance for their brothers and sisters to accomplish their mission in their sted.
Brutally, one by one, they were killed and captured by Nidhog's tentacles, but at least one of them managed to reach the back of the monster's neck, as the tentacles continued to sprout from the monster's body and try to get him he managed to survive, quickly arming the explosives he was carrying and run across the still opening maw of the monster by the looks of it the outer mouth was now about 40-meters apart and the three surges of electricity were more erratic, surging with much more power, similar to being dangerous close to a Power Node of space hulk, so now instead of dodging tentacles the guardsman was trying to evade litteral thunder and electricity all around him.
Just when he was about to reach the center of the head and drop the bomb, deep burgundy colored multi-barbed tentacles came sprouting out from within the outer mouth of Nidhog in truth these were tongues from the inner mouth sending the human like a tiny insect crawling all over it's head and as a result Nidhog struck back with it's tongues that managed to wound the human, the barbs that covered the tongues cut and shredded deeply into the flesh of the guardsman the wounds were so severe that he couldn't move as fast which eventually led to his explosives triggering, blowing up right on top of the Nidhog, this of course caused it great pain especially from the area that the explosion occurred, roaring from the pain as it retracted its tongues but refused to stop its incoming attack.
Their last ditch effort to stop Nidhog failed as the charged amount of power was now a ball the size of Armiger Imperial Knight now with swirls of purple along with the violet and black seems that the only way that Atlas Primoria, could hope to survive is the shield being able to willstand against the incoming attack.