Sathiidism arrived on Earth just years after the Advent War ended. In order to secure it's superiority over Earth, Aempis needed a source of Meta which generations to come could rely on—Monoliths, who also tended to be Sathiid to offset the demands enlightenment took upon their bodies.
As Jhoutaioan history repeats, often, with gusto: Sathiidism likes to spread. Bodily fluids are its favored vector and, whether it's a thousand kisses or a dozen bites, it will get around. After the famines of climate change and the ravages of alien conquest, the spread of a disease that turned humans ghoulish with a bottomless hunger felt like the arrival of Famine.
It was in this darkest hour of humanity that the Bleakhearts were born. Not as saviors—no, but as the saved. Some of those who came back from being ghouls returned with a scar upon their blood, something which lurked within them.
They are often shunned as a people, as their mutations can make them dangerous and uncontrollable. Many fear them, but others sympathize with them and accept them for what abilities they bring to the party.
Though Firstheart in basis, most undergo their first mutation when puberty is entering full swing. What this mutation is differs from Bleakheart to Bleakheart, but the first is not usually very drastic. Bleakhearts are more often lithe in appearance, a result of their mutations jumpstarting their natural metabolisms.
As a BleakHeart ages or undergoes stress their mutations will worsen and their bodies will become more alien. The ultimate fate of any BleakHeart is to become entirely monstrous in body, spirit, or both in a process known as blooming.
The Church of The Somnolent, which tends to protect and help them.
The Federation of Free Planets, which tends to exploit them as a lower class.
The ValuSelu Pact, which has few places for a creature without a purpose.