There were two very different breeds of Thwog. The Thwogs native to Ardolis tended to hang upside down from the cave cealings much like a bat and attack Ratchet from above. They could generally be easily defeated with a single strike from the OmniWrench 3000. But the Gore Thwogs from Merdegraw that lived in the far darker Morrow caverns had glowing red eyes and swarmed so intensely that it was impossible for Ratchet to destroy them. The only way to get past them was to scare them away with light from a Helio-Grub.