Its appearance is similar to a large centipede. It attacks by jumping out of the sand in the Oil Desert Zone. It has the same name as a previous robot and a similar color scheme to another. Sandworms also have a more violent-looking appearance.
Sonic 4 Website info
A newly developed large Centipede type Badnik designed for use in desert areas. You never know when they will suddenly emerge from quicksand, and be mindful of its robust body that is resistant to attacks.
Sandworm is the second badnik that appears in Sonic the Hedgehog 4: Episode II to be a different badnik with the same name as a previous one. The first was Spikes.
Sandworm is also the only badnik in Sonic the Hedgehog 4: Episode II that is resistant to every type of attack.