Spontaneous Generation
Spontaneous Generation is a perk that causes vomit near you to transmuted into Ratty Powder. When released into the world, Ratty Powder will immediately be removed and has a chance to spawn a Ruttorotta (plague rat) which will last for just over 13 seconds before vanishing. A maximum of 30 plague rats can be summoned using the powder.
Additionally, this perk spawns a flask of vomit potion when you pick it up.
Tips
Generally, this perk will have middling effects, as vomit can be somewhat uncommon to come by consistently. With a lucky Fungal Reality Shift however, you can convert a more common liquid, like water or oil into vomit, increasing the consistency of this perk. Fungal Shifting blood into vomit is especially effective, as most enemies will bleed vomit that can be turned into rats. This stacks especially well with Plague Rats and More Blood, summoning even more rats.
Transformation
When you have Spontaneous Generation, Plague Rats, and Revenge Rats, you will be granted the Ratty Transformation which causes you to grow a rat tail and gain a 15% boost to your horizontal movement speed.