You can find the source of anything in the game in the Access Info tab, you can scroll over to it after opening the map. As for Lethal Infection specifically, I'm not really sure what the best place to get it is. I think I got mine while Obstructor farming. I know the non-elemental reactor in Vespers Moonlight Lake has a 5% drop for it on completion and might be a decent option if you have a good valby build or something.
What is the easiest farm for it?
Where is the best place to get it
You can find the source of anything in the game in the Access Info tab, you can scroll over to it after opening the map.
As for Lethal Infection specifically, I'm not really sure what the best place to get it is. I think I got mine while Obstructor farming. I know the non-elemental reactor in Vespers Moonlight Lake has a 5% drop for it on completion and might be a decent option if you have a good valby build or something.