The Grubs are larvae-like creatures, emitting a high chirping call and bioluminescence similar to that of a firefly. They are found only deep inside Antlion colonies, and can be seen hanging on any available surfaces, often in groups of two or more. They are extremely fragile and can be killed by merely bumping into them. In the hive, human remains are sometimes found scattered on the ground near Grubs, suggesting that they are carnivorous and are presumably provided with food by mature Antlions. Grubs also exude a filmy thread, similar to that of a but on a much larger scale. As seen in the Victory Mine, these webs often blocks whole passageways or contain items useful to the player. Every Antlion in the nest will protect grubs fiercely.

Grubs internally contain a yellow 'nugget' substance with healing properties. Killing the Grub releases said nugget, which varies in size (it includes three models: small, medium, and large). How much the substance heals is dependent upon the players' current health level.