The swamp-dweller boy Stassi used a swamplands slug called Zrath to move his sled.
The swamplands slug look like a vast, grey, glistening slug, except it has two great black-spotted humps that rise in the middle of their back. The black spots its humps are able to darken and spread. Their eyestalks are as thick as a human's arm. Its bloated body is rippled. They excrete a silverly slime.