Spriggan
A type of small Scottish rock goblin that has the ablility to inflate itself to giant size. Also a form of elemental that can present itself as a large male cat.
As Heather picked her way across the ridge she saw a tiny, wizened creature dart from beneath a boulder, pick up a stone larger than itself, and even as it raised the rock above its head it grew..and grew...and grew, until it stood on the ridge like a huge, twisted oak.