In Warhammer, I Am Sanguinius

I transmigrated into the Warhammer world. My superior is a towering, golden giant. Through some mysterious means, others gradually become my bloodline descendants, growing more like me over time. They suffer from the Red Thirst. Their preferred color scheme is red. They stand opposed to the four Chaos Gods. And there is the keyword: Emperor of the Second Empire. So who am I? I realize it—I am Sanguinius! This is a Warhammer Fantasy (not 40k) story, with over a million words already written—feel free to dive in.