The Choomahviathan was an enormous Choomah formed out of the initial Choomahs that were part of Dr C.'s research, that uncontrollably grew inside a pit after it was accidentally dropped. Formerly an Island in the South Pacific, it became a living organism when the Choomahs first started growing. Over time, the island mutated into a monster similar to the ones that destroyed Kingdom Cum. Hundreds of smaller Choomahs were created by the experiment as well in an area referred to as the Choomah Hive. The Choomahviathan remained dormant, until Leslie Mackerel and his gang attempted to destroy the Choomahs for good. After the Choomah army was defeated, the Choomahviathan awoke and attacked. After crushing Daednu with its hands, it attempted to kill the gang, but was destroyed by Clarence with a SasM8 in a sacrificial attack.