These incredible figures of Tyrael and Diablo himself are the work of an avid Diablo fan, TaeHyeon Hong from South Korea and he made them out of nothing but paper.
Hong used something called the kirigami technique, which basically involves cutting up pieces of paper and morphing them like origami figures. It's how he created this superb, faceless Tyrael (whose sword, the El'druin can apparently even light up, due to a light reflection off the white paper would be my best guess) and the really detailed Lord of Terror.
Here are a few more photos from different angles:
The Papercraft of TaeHyeon Hong [Battle.net]