Total War: Warhammer III

As Nurgle you'll mix plague traits to infect you own settlements or armies which then infect bordering enemy settlements and gives them negative effects. Some of these traits you'll research but others you'll need to spread a base trait 50 or so times. It will tell you what you need to do and how many times you have left to spread its base trait when you hover your cursor over a trait that you have yet to unlock. Plagues spread much fast than you might expect. This achievement might not unlock as soon as you get all the traits. I had to reload my game and pass 1 turn.