Context: A Titan princeps is "dreaming" about a contest in her past, when the Knights on her world tried to win the favor of the Mechanicum. She was supposed to be spectating, but decided to grab the prize for her house when she saw the chance.

Against the weapon’s conical guard rested the day’s favour, a tilting hoop large enough for a warsuit lance to snag from a target hook. It was made of brass and toothed like a cog. Whoever carried it to the finishing post would win the greatest concessions from the machine priests in the coming negotiations.

Some descriptions of the Knights and them fighting for the cog

Whistles shrieked. The Knights slowed, ponderous heads seeking out the fallen prize with primitive autosenses. Mohana saw it first. It bounced over the short grass like a live thing fleeing a predator. She watched it hit a lump in the ground and take off, toothed edges flashing in the sun.

Before she knew what she was doing, she set Hamaj into motion. The stallion lunged towards the prize. The cog was rolling along the ground, leaning over, about to come to a circling stop. Mohana swung low off her saddle. Rushes whipped her face. She reached out and grabbed the cog. It was almost too heavy for her to pull up, so she twisted, sending Hamaj veering sharply to the right, and used his momentum to sling herself back up into her seat.

She hung the cog from her saddle pommel and leaned into the wind.

‘Fly, Hamaj, fly!’ she breathed into the horse’s ear.

...

She was winning. She was not supposed to.

The craft was bigger than House Vi’s fortress, a hundred metres high, its sloping sides emblazoned with the off-worlders’ strange heraldry. Most prominent of all was the divided skull they bore on all their gear and clothing, stamped into the panels on all sides of the ship. Its machine smell was acrid, far less welcoming than the warm scent of the steam engines that powered the Knights. And yet she raced for it with total abandon. She had crossed a line. There was nothing else she could do but see her actions through to the end.

The rattling-pounding of Knight footfalls drew closer behind her, too late. She flew under the arch and drew up her horse before the dais, in front of the great ship.

...

Mohana lifted up the heavy cog in both hands and showed it to them all.

‘In the name of House Vi, I claim the patronage of the Mechanicum of Mars, and the favour of the forge world of Tigris.’

She threw the cog down onto the bare, baked earth. She might as well have dropped a bomb.

Her father’s position was compromised. He could not rebuke her, because he would throw the whole contest into doubt, but if he backed her actions, he disrespected his dukes. Either way, the honour of House Vi was at stake. His cold stare promised terrible punishment. The royal court was aghast. They goggled in disbelief and muttered behind their hands. The blank metal and flesh visages of the Mechanicum delegation could not be more different to those of the court of Procon. Blends of machine and man observed her clinically. Lights blinked in place of eyes. Lines of text streamed over glass displays set into chests.

‘Interesting,’ said the representative.

The king looked to his guest, unwilling to make the first move.

‘This contest is void,’ said the duke of House Kandaj. ‘This was to be a display of the skill of the Knights, not of horsemanship!’

‘The Knights’ skill was lacking. The huntress has won,’ said Mohana. She could say nothing else. She was terrified. She should not have run with the Knights. Her split-second decision to take up the prize would cost her life.

The dismay of the court grew. Knights were coming to a stop around the arch, steam roaring from overheated engines. Cockpit hatches slammed back. Warriors tore the interface cables of their thrones from their necks to stand proud in their cockpits, and condemn her from on high.

‘My daughter shows great courage, and resourcefulness,’ said the king. ‘She has shown us all up!’ He laughed indulgently, though any that knew him well would have seen his humour for a lie.

No one else laughed. A heavy silence fell, subduing even the wind. Strange machine chimes and the rattling of mechanisms sounded from one of the Mechanicum delegation. A disturbing twittering, similar to but horribly unlike that of birds, passed between several of them.

The representative was the first to speak human words. ‘I say she has taken the token, and she has won,’ he said. ‘I proclaim House Vi victorious.’

From their expressions, the nobility had expected the Mechanicum to cry foul, but the machine priests did not seem in the least perturbed.

The Mechanicum is pretty much known for making analytical decisions rather than allowing human emotions and thoughts to guide them, and this is a great example of them just not giving a flying frick about everyone's customs, because they're not beholden to those whims.

Bonus: Her father gets one-upped (this is from the POV of another princeps)

Her father – who was the king, by the way – Rahajanan, thought he could exploit them in return. Part of the exchange was to be a tithe of young nobles to go to Tigris. Rahajanan saw the opportunity to save his warriors, and so offered the daughters of his house instead. He thought he was being clever. His daughter was troublesome. His Knights were valuable...He thought he had tricked the red priests and saved his best warriors for himself, selling off his house’s daughters in their stead to who knew what fate. He did not care. He kept his Knights. They gained the technologies of the outland men. What did it matter to him if it cost him a few women?’

The smile she gave him now was less mocking, more of pleasure. ‘It did not matter to the Mechanicum of Tigris whether the Knightly houses provided males or females. They required good gene stock with proven compatibility with mind impulse units from a politically neutral source, that is all, and so the Great Mother’s bitterness at her exile turned to a grim delight as she and her sisters were trained as the mistresses of a new Legio of god-machines.

‘When she returned to Procon several years later, her father had to kneel before her. I imagine she laughed to see that. His vaunted warsuit was a child before the machine she ruled. He had played the cunning king, and unwittingly elevated his daughter to godhood.’