A Pure Lifer, whose ancestors had been some of the earliest of the Pure Lifers had gotten very, very sick. They were still quite young, had very small children to raise, and none of the "medicine" on their world was helping them. In fact, they were getting worse quickly, and no one was willing to care for the children if their parent were to perish, and they had no spouse. What were they to do? Only option left, contact the Alliance, it was, quite literally, life and death, for their entire family. -- Lessons
It was their choice to go and be pure. It was their choice to build a world without the vaguaries of big pharma's conspiracy potions, or technology that they couldn't find. Or, most importantly quote-unquote 'medicine' with ingredients they couldn't pronounce. No toxins, just nature and healing from a pure world.
Life was short, after all. On Neoden, it was even shorter than it had to be, but by the divine powers, it was natural. Some even shunned antibiotics, preferring homeopathy and essential oils.
The way to make everything work quickly turned into, "Have plenty of children and hope that some make it to create the next generation." For Lysaa, it was the Pure Way. Eat clean, purify the home with cleansing scents and incense, have the right crystals in the right place and all would be well forever. Except... it wasn't.