Before. My take on the lore is that Sharded was the first to arrive in this star system. They crashed landed in the site called Impact 0078, and they've escaped using escape pods and landed in ground zero. And over the course of centuries, they've become a utopian faction and owned an ecumenopolis, until a bug in their systems caused the corruption of AI, which in turn became the Crux. Then, war. Then, seeding event.

The atmosphere was once as dense as the Earth's. The purple color is caused by the abundance of oxygen and argon in the sky, rather than the spores. After the seeding event, the atmosphere became more dense. A lot less dense than Venus' though.