Its the infestation markers

the others are such comedians...
he's a new kid, cut him slack dammit!
As for the infestation markers, as far as i know, they do jack all, but they make for some great themed terrain, objectives, and anything else you care to think of. I for an example used the teethy bits to make something like a giant flea?
Also, you can use them on your ripper bases.