Kyren

The Kyrens were a crystalline species hailing from the Great Ice Shard, where they served as the warrior complement to their cousin-species the Kyresa. When the Great Ice Shard was destroyed, a Kyren invasion force led by Noble Commander Crydax began an attempted occupation of Earth, armed with a new weapon, the Fragmenter. This invasion force was ultimately defeated by the Doctor and Emily Whitaker, who used the Kyren Fragmenter on its creators.

Kyrenk Empire
Details of the Kyren system of government are scarce, but Noble Commander Crydax's attempted invasion of Earth was to provide the Kyrenk Empire with a new seat of power.

Physical description
Crystalline entities, the Kyrens were rocky in appearance. Within crystal skulls, they had glowing orbs, which pulsated when the Kyren was in pain. Roughly humanoid in shape, their forms were marked with jagged edges. They proved immune to human bullets, though they could be temporarily stunned by them. It appears that at least some Kyrens had an ability to detect the species of creatures they interacted with, as despite her shimmer device Emily Whitaker was identified as Korina rather than human. Given that neither Noble Commander Crydax or his officers noticed this, it could be that the ability is uncommon among Kyrens, or was aided by technology.

The Kyrens' main weapon of choice was an energy weapon which had the ability to disintegrate humans. This weapon fired a blue beam.

Naming
There is confusion as to the name of the species, owing to a discrepancy in their presentation. In the first part of The Winter of Discontent, they are consistently referred to as Kryens. However, in the second part they have become Kyrens. It's uncertain whether the Kyresa are affected by a similar inconsistency, as the first part of The Winter of Discontent remains the only published piece to mention them.