Coretoise resembles an Earth tortoise. His skin is dark yellow and he has three claws on each limb. His brown shell is dotted with cracks filled with a magma-like substance. His abdomen is covered by a brownish skin.
The Omnitrix symbol is located on his chest.
- Heat Resistance- Coretoise can withstand extremely high temperatures.
- Magma Generation- Coretoise is able to produce magma-like substance and either spit it or erupt from their shell.
- Rolling- Coretoise can pull himself into his shell and roll around, scorching the ground.
- Vulnerability to Water- Coretoise can be harmed or even killed by being poured with water.
The Testuvians are a peaceful race inhabiting a planet with numerous volcanic islands littering its surface.
Despite their abilities, they are still often a prey for the Caldeian Pelicanuses, which scoop them off the ground and fill their bills with cool water.