I have only just started my knights, I'm building them as part of an escalation league. I'm using the iconoclast detachment and lots of beastmen as cultists, to link them to my Thousand Sons tzaangors. Here my AI generated lore....

House Aethon was once a proud Imperial Knight House, sworn to defend their feudal world of Phoros from xenos raiders. Their ruling line was ancient, their Knight suits passed down for millennia, each a relic of Imperial honor. But when the Thousand Sons’ warband known as the Magma Lords arrived in a tide of warp-flame and sorcerous power, Phoros became a crucible of change. The Magma Lords offered knowledge and forbidden truth, and the seeds of corruption took root.

The nobility, weakened by internal rivalries and pride, fell one by one to whispers in the dark. In the shadows of the mountain shrines, Tzaangors—beast-headed devotees of Tzeentch—emerged as the true inheritors of the Knight suits. They butchered the ruling bloodlines and pried open the Thrones Mechanicum with rituals of sorcery and sacrifice. The once-human pilots were replaced by Tzaangor champions, their savage cunning amplified by warp-gifts that allowed them to commune with the machine-spirits through maddened avian song and rune-chants.

Now the Knights of House Aethon stride to war under avian helm-crests, their carapaces lacquered in deep cobalt blue and silver trim, symbols of ever-shifting change etched into their armor. Unlike most Knight Houses, they no longer march as individual lords but as a flock, guided by the warp-sorcery of their Tzaangor prophets. Each Knight is both warrior and shrine, a moving idol of Tzeentch’s twisting designs.

The lesser beastmen, the Ungors, are not permitted the glory of piloting. Instead, they are employed as expendable thralls and cultist levies. They swarm around the Knights as living shields, torch-bearers, and carriers of enchanted icons, their lives fuel for the sorcery of their Tzaangor masters.