Helblindi:
So, I suggested this idea before in describing how my dwarf/chaos dwarf throng got along with each other. Some people seemed interested, so I thought we could discuss this more deeply here.
I’ve done a minor bit of lore checking, and I found here that Grimnir entered the Chaos Realm in -4390 I.C.
On our own wiki, I find that the worship of Hashut started at around -4000 I.E, so about 4 centuries later. Time enough, I would think, for chaos to succesfully corrupt Grimnir, maybe even merge him with a daemon, or something alike. In any case, the typical dwarven characteristics (lust for gold, mining and forging skills, talent for technology) would become warped and merged with more chaos-like qualities (urge to dominate and subjugate, cruelty, daemonbinding) into a diety now known as Hashut.
I’m not exactly a lore expert. Are there any other arguments for or against this theory that I’m overlooking?
cornixt:
It’s been speculated on before, but there just isn’t much more than the circumstantial evidence you already have.
Abecedar:
Don’t need evidence, just ask any religion. All you need is belief
Admiral:
This is a good take on it, and certainly conceivable. Makes for great niche cult background in particular! IIRC Grimstonefire touched upon this possibility in his WIP Liber Chaotica: Hashut. While I personally prefer Hashut to be a minor Chaos deity/Daemon on his own, the Grimnir connection have a great strength in explaining the tribal connection between (Chaos) Dwarfs and the Father of Darkness, and at the very least it makes for great Liber Chaotica-style speculation. After all, no one else than corrupted Dwarfs worship Hashut as far as we know, so this idea makes a lot of twisted sense, or even variations on it such as a fourth fallen Ancestor God never more mentioned and forgotten under layers of aeons and censure by uncorrupted Dwarfs.
One could even argue that stout corruption-resistant Dwarfs could never truly have become corrupted unless by their own Ancestor God. Grimnir remains a prime suspect.
As a vanilla Dwarf player first and foremost, this idea rings particularly heretical to me, which is a stark bonus. Dark secrets indeed.
Good idea here, Helblindi! :hat off
Last but not least, this idea resonates so well in a cyclic way with the gold-winning entry #5 in Scribe’s Contest III and its casting off, at the end of days, of all ostentatious demented corruption inherent in the cult of Hashut and the wider ruinous forces worshipped by the Blacksmiths of Chaos:
A Slight Return
The sound of Zharr-Naggrund�?Ts great furnace exploding rang through Daemonsmith Hzzkad�?Ts private chambers. It drowned out the howls of the Greenskin horde assailing the great capital. The demented screams of the K�?Tdaai unleashed from the bowls of the ziggurat in a final, desperate counter attack. And for a second it even obscured the crack of fireglaives coming from the corridor just outside, as the handful of Infernal Guard allocated to Hzzkad�?Ts protection, made their doomed, final stand.
Hzzkad had barricaded himself in his chambers at the first sign of trouble. He had seen the end coming. Watching the skies through the thick clouds of toxic smoke that perpetually hung about Zharr Naggrund, he saw the subtle changes in the stars as the sickly sheen of chaos spread across the world. The Prophets dismissed his fears as weakness. Those same Prophets who were now in the grand chamber, desperately spilling the blood of their own Bull Centaur retinues in a hopeless attempt to summon Lord Hashut to save them in this dire hour. Hzzkad knew Hashut was not coming. He knew that the great capital would fall. Death did not scare Hzzkad. What came next terrified him.
Ignoring the sounds of battle Hzzkad stood facing the giant, polished plate of brass, screwed to the wall of his chambers. He saw his terrible reflection. The tiny horns protruding from his head. The twisted, stone stump where his left arm used to be. The single, grim tusk that erupted from his jaw causing his lips to loll open in a permanent sneer. Trophies of heresy. In his one good hand Hzzkad clutched a saw. Forged of base metals but sharpened to a surgical edge. He had used it many a time in the rituals. Sawing off the head of a still living sacrifice. Pain and terror spicing the blood for Hashut. Gritting his teeth Hzzkad began to saw at the first of the two horns. Part stone, part tissue every draw of the saw was burning agony. Hot, coppery blood poured down his face. But still he continued until with a wet, wrenching plop the horn fell to the ground. Hzzkad paused for breath. The pain worked him, exhausting every reserve he had. But he was not done. With grim determination Hzzkad hacked the second horn from his head. Blood gushed from his wounds, staining his face a slick crimson. Hzzkad inspected his reflection. He ran a hand across his smooth forehead. And in the midst of the pain he smiled.
Putting the saw down he turned to the other tools he�?Td gathered for this moment. Hzzkad picked up a pair of pliers, still mottled with the dry blood of whichever slave had been too quick to stumble or too slow to move. A slave just like the thousands who right now were exacting their well earned revenge on his fellow Dawi Zharr.
Hzzkad locked the pliers around the tusk protruding from his mouth and closed his eyes�?�
He pictured a cavern, lit by warm braziers. He heard singing and drunken boasts. He smelt meat roasting and ale, rich and hoppy. On the cavern walls he saw the shadows of comrades in celebration. Proud, boastful and true. A blood bond thicker than any incantation�?�
Hzzkad gripped the pliers and pulled as hard as he could.
The sound of a battering ram crashing against the door brought Hzzkad to consciousness. He lay on the floor, his mouth filled with blood, the ugly tusk lying beside him. There wasn�?Tt much time left. Scrambling to his feet Hzzkad rushed to the sealed chest he kept in pride of place in his chambers. A chest without seams or joins. Even the mightiest giant could not pry it open. But with one touch from Hzzkad the lid gently lifted to reveal its secret.
Hzzkad lifted up the solid, double headed axe. He admired the runes upon it. Runes he could no more understand than he could alter the fate of Zharr-Naggrund. The doors were beginning to give way but Hzzkad was ready. His horns and tusk gone and in his hand an heirloom passed down through his bloodline for generations. A secret shame held by his kin. A reminder of a long forgotten past. As the doors began to splinter Hzzkad became aware of the corrupted, stone stump of his left arm. A final mark of guilt. With one mighty strike Hzzkad brought down the axe on his deformed arm, shattering the limb in a hail of stone and blood. And finally, he was whole.
Axe in hand, a half remembered song about drink and kin and glory on his lips, as the horde outside surged through the doors, Hzzkad stood his ground and prepared to die like a dwarf.
TimothyLeighton
Nicodemus:
I too would love to see Grimstonefire’s Liber Chaotica: Hashut completed as well, and updated with artwork and some photos of models and chaotic landscapes, etc.
One day.
Admiral:
We’ll whip him to it if we have to! 
There’s an ever-increasing wealth of fan artwork produced here, and ever more background written, so it should be easy to find illustrations/illustrators and inspirational sources whenever the scribal master returns to his masterpiece. Eagerly awaiting the next instalment. With patience.
Helblindi:
Too bad, I was hoping for some hidden lore spicing it up 
Fortunately, no evidence is needed to start a cult, and the more cults (like the one of the false cucumber), the more reasons for wars and rebellions.
The story is indeed fitting, a far racial memory of a distant past.