Storyboard.
The Terrorpede is a giant, nocturnal creature of the mist. It was seen in storyboard art for The Mist but wasn't featured in the finished film.
It has huge, claw-like antennae with red tips, supposedly from biting into something. Early storyboard art for The Mist showed a Terrorpede crawling into the Food House through the window hole on the first night when the Pterobuzzards breach the store.