Vanarx

The Vanarx, or "Yeerkbane," is a creature that feeds on Yeerks. It resembles a long, thick, purple tube that ends in a mouth filled with thousands of tiny suckers. The Vanarx is also able to eat Yeerks that have fled into a host body. It attaches its mouth to the head of the host, and sucks the Yeerk through the ear canal. It is unknown whether this causes any temporary or permanent damage to the former host. Visser Three possesses this creature's DNA, and takes video of himself punishing his underlings with the morph, so he can play it back later with the intent of frightening his underlings into success.