(General POV)
Location the Warhammer 40k World-The Immaterium: The Neutral Zone of Chaos, the Mount Olympus
After...whatever amount of time, or what counts for time passing in the Warp as, the Arkefine, Vashtorr, he sent a psychic message to Laharl, Khorne, Nurgle, and Tzeentch that he wants to speak and finally...negotiate with each other.
After that call the older Chaos Gods, have immediately prepared to go to Olympus, and greet their new brother face to face, as for the offering that Laharl Valboga was about to suggest that not only Vashtorr join them.
Offering the Arkefine some machine creatures, that can serve as new daemons in the legion of machine, from the Geth from the Mass Effect series, the classic T800s Terminators acting lesser daemons and combat force of the Vashtorr legion, plus from XCOM2 two creatures can serve as Vashtorr's high-daemons, those two choices being the Codex, and the Gatekeeper.
But also a couple suggestions for Elder Daemons Left & Right Twins, from the Atomic Heart, they can act as the assistants, for Vashtorr, as well as bonding them both to each other and Vashtorr himself.
Next it is Megatron the leader of the Deceptions, he can even offer a bonus of a massive daemonic-machine combiner composed of various variations of Megatron, with Gun-Megatron, T-Rex Megatron, Tank Megatron, Prime Megatron, and Cybertron Megatron, all mainly connected to one single conscience, obedient and loyal to the Chaos God of Machinery.
With Left & Right they'll serve as guardians and direct support beside the ever creating and working for the Arkefine's deeds, and Megatron can serve as a commander and general for Vashtorr's ever expanding legion.
Knowing Vashtorr...from small lore that Laharl has access thanks to GW, Vashtorr loves efficiency, so offering that with all these various potential cybernetic killers and beings, they'll make quite a impact and for a added incentive.
The Dark One, plans to offer lastly Sovereign the a high-ranking of the Reapers from Mass Effect.
That advance planet ender, daemonized and ascended to a level of one of the 40k, like a weapon of galactic destruction that...for some reason the most that possess weapons of that caliber in Warhammer, are the good old Necrons.
As Laharl appeared in the golden palace that once belong to the GOW-Olympians, he was soon joined by the eldritch ever-changing Tzeentch, then all the corrupted flowers in the wall scouns, started to wither and rot.
Suddenly both the Carnage and Change Gods, turn to the side through the hall, and saw their brother, the Corpse God, Nurgle, who laughed and coughed, then surprisingly rushed over and hugged them!!
Tzeentch most of the two previous Dark Gods, was more shocked at Nurgle's affectionate gesture.
They could barely stand the stench, and miasma that whasp out of Nurgle's body, as Nurgle expressed his joy of seeing them again.
While Tzeentch was confused...and very disgusted, a bit iratated at Nurgle's affection, and Laharl just expressed, he was happy to see Nurgle again...and for Plague Lord to put Tzeentch and him down, which eventually Nurgle did.
Nurgle, started talking to Laharl about their kids, as Tzeentch set himself on magical fire, not to harm himself but to get the stench and filth off of himself, groaning angrily at Nurgle, as the last to join them was the Blood God, Khorne.
He saw Tzeentch on pink and blue fire, and shuke his helm head, as he said in a slightly...well for Khorne...annoyed sounding tone, "I don't even want to know." Nurgle greeted him first, and as he approached the Blood God, and all Khorne did was raise his right gauntlet, igniting in hellfire and shaking his head at Nurgle.
Nurgle, he raised his hands in mock surrender, and laughed like his usual self, as the four of them, exchanged pleasantries and started heading towards the Dinning Hall, so they can wait for the final Dark God to join them...
Location the Forge of Souls, the Throne of the Original Heretek-z
Vashtorr, was getting ready to leave his realm, after letting his...brothers, in waiting for quite some time, he seems more than ready to proceed with these..."peaceful negotiations", with his fellow Gods of the Immaterium.
Standing up from his throne, all his daemons respectfully and obediently, got away from their standing dark divine lord, with a simple gesture of his "organic" hand his Hammer of the Soul Forges, appeared in his grip.
Spreading his brass and metallic bladed wings, he started walking forward, stepping through his ever expanding forge, working on flesh, metal, and soul making more and more things of infernal nature, with venomcrawlers, husk exos, and servants of the silent ones, all crawling around the forges, smelters, and many more machines, as the daemons were making robotic, and monstrous sounds.
Vashtorr, vox/gas mask piece on his mouth, letting out a robotic like chuckle, as he adores this reverence done by his ever growing number of daemonic servents.
After stepping out the limits of his personal sanctum, within the Forge, he bashing in a burst of Warp-energy, leaving behind a black whisp of sulphur, and motor oil, as the Chaos God of Machinery has for his first time, since birth left his realm.
Location the Mount Olympus-The Palace of the Dark Gods; the Dinning Hall
A bit later, in the golden, majestic dining hall of the Chaos Gods, Laharl, Khorne, Tzeentch, and Nurgle were waiting for Vashtorr, sitting around a God sized, golden table filled with various dishes fitting all their preferred style food.
And lots, lots of Ambrossia, again in their preferred taste, they were just passing the time bantering and enjoying their meal.
That's when the scent of a smelter, burning oil, and smoke, just like a forge, as Laharl saw the iconic robotic daemon entity, looking exactly like his model of GW, with his massive claw/melter attached on the claw's palm, that grayish, withered body.
Vashtorr, he scanned the room and after satisfied from looking around, and feeling the surge of Warp power, across this palace and mountain, it impressed and intrigued the Arkefine.
Then he spoke in a radio or vox chatter, "I'm impress with all the power surging through this facility. Quite intriguing. Plus this proportion, that you're Elder Daemon sent me. You all are interested in bargaining?" Tzeentch started cackling, as he'd respected Vashtorr's inquisitive nature.
Nurgle chewing on some nato pasted, very dried aged steak, laughed and enjoyed himself, spitting out maggots, slug, and sickly dark green drowl, Khorne greeted Vashtorr...in his own way...by raising his skull chalice made from Ares' own skull, to drink redrum ambrossia, and Laharl offered Vashtorr a seat.
Which after some considering, Vashtorr finally took a seat, not interest in food...but he was surprisingly drawn to the scent of the liquids, that all four older Chaos Gods were drinking.
Laharl noticed a slight shift of expression, from Vashtorr and snapping his claws from his clawed-power gauntlet, a mortal without eyes and baring several eightpoint-stars on his body, offered a massive gold cup, filled with Ambrossia to the Arkefine.
The Dark One, explain its pure liquidfied Warp-energy, quite delicious and refreshing, insisting to Vashtorr to taste, even stating it might become something he'd might indulge more in the future, should he try.
Taking the cup, his scent detector, indicated nothing was amiss or harmful in this beverage, and deciding to indulge in this offering.
He closed the cup to his face, as a bunch of steel like, flexible, and highly robotic tunes, came out the side of Vashtorr's "mouth" and entered the transparent lavender and violet colored liquid, as he drank.
All his detectors, and organic senses were hit with a great sensation, seeing this made Laharl laugh, as Khorne growl in frustration, as Vashtorr heard something of a bet between the Blood and Carnage Gods involving him enjoying Ambrossia, as this display is quite strange for Vashtorr.
They are Gods that embody, various aspects of extreme emotion and chaos, and they act...they act like an actual family, over rival for power...it was confusing in all honesty for Vashtorr.
Regardless, after everything was settling down, Laharl spoke, "So little brother, shall we start, talking business? Or do you want another cup of ambrossia?" Vashtorr replied, "It would be crucial to begin, the purpose of this meeting...and yes I'd would enjoy another cup...my appreciation, Dark Harbinger." and with that their discussion started in a smooth fashion.
Laharl told the benefits of joining them in a truce, along with binding himself, Nurgle, Tzeentch, and Khorne to a oath, to insure their integrity and prove their words to Vashtorr.
So returning to those benefits, absolute security of his domain, all issues, challenges, scuwables, games handled in Materium, either on some planet that they need to corrupt or on the Anarkarr Stars...which the older brothers, will explain "that" to the newest one later...along with access to many great things, secrets that he couldn't image.
Such new great additions for his legions, this caught Vashtorr's interest, and he'd made a gesture to proceed, Laharl smiled, and after taking a swing of his ambrossia, he said, "So let tell you of Terminators..."