Attention! You can buy him!
http://www.dota2.com/store/itemdetails/10298?r=258

Orphaned and abandoned on the fringes of the Nightsilver Woods, Waldi was rescued by a reclusive band of rangers and trained in the ways of war. Waldi is often underestimated by his foes, but his unassuming appearance belies his relentless tenacity and unfailing loyalty. He is a worthy courier and companion for the mightiest of warriors, a true dog of duty.

Base Story: Ian Dorsch
2d Concept: Adina Krause, Johannes Figlhuber, Steffen Unger
3d Asset: Steffen Unger
Animation: Jochen Volz