There are several rat types you can achieve. If you feed your rats,they will grow until they reach the next level. You can also mix rats and speed up their growth, we will cover this in another article! Let's get an overview:
From level 1 to 5 your rats are grey servants. They are weak but effective in numbers, don't underestimate their punch!
From level 6 to 10 your rats grow up to stronger purple rats. They think they are something special, because of their shiny crown. No one knows exactly, where they got it from. Purple rats are mean but sometimes lazy.
From level 11 to 15 rats are angels. But they are far from being holy or devout! Sometimes they have the munchies for a special snack...
From level 16 onwards your rats are devil rats. Strong and angry, they can cause severe damage. But you have to feed them well and they also come with a special wish...