Board Thread:General Discussion/@comment-26261619-20150331024349/@comment-26284218-20150331105037

The answer could be as simple as Lion not surviving by going through photosynthesis and not producing any oxygen. Like @Painite said we don't really know how his pcket dimension works.

Also Gems don't need to breathe so there'd be no need for air his dimension. Steven not being full gem would obviously not be able to breathe somewhere without air.