They come with the banners, champions sprue. I think they should go on a banner pole as an icon possibly. I think they make a good champ for the rats. There are 4 spruces so there should be one more lurking around. I was looking on the Warscroll for the monks and there kinda fun with their books and scrolls. The giant rats have 1 attack hit 5 wound 5 but if you have 20, you have 2 A, 4hit 5 wound and if you have 30 3A,3H,5W
Again it gets into crazy horde numbers. I was reading one list where the guy has 3 units of 40 clanrats and 20 stormvermin. That’s a pile of models.