Version 0.3.996a(d)plus theres not much to it right now.. collecting yuna takes forever, you could kill 50 symbiotes and nothing will show up, so the "corruption/transformation" aspect i won't experience.
> Added in-game wiki/guide
As the number of defeated enemies and collected loot increases, the level of infection increases.
When the infection level is high, events appear.
Lots of Yuna drops from crystal event. There are very, very many enemies.