What is Jund in MTG?

Jund is a setting in the fictional universe of Magic: The Gathering. In the game's lore, Jund is one of the five shards of Alara and is primarily aligned with the color red, but green and black act as secondary colors.

The shard of Jund is littered with active volcanoes and ruled by powerful dragons. As such, life there boils down to survival. The word "Jund" could also refer to a type of mid-range deck constructed early in the block's rotation. It was considered a very powerful deck through its mixture of red, green and black cards and quickly rose to dominance in the competitive scene.