Gelfling

This is going to be the Grunok of Thra.

The crimes of the Skeksis are many on the planet Thra, from the cracking of the Crystal of Truth to their war of extermination against the Gelfling.

While the plight of the Gelflings is of particular note, other species suffered and died under Skeksis rule, including the gentle Grunok.

As related by Adam Chessery in the Dark Crystal Bestiary, these gray-skinned, flat-faced bipeds were a prominent, technologically advanced sentient species on Thra during the Age of Harmony.

But as the Skeksis rose to power during the Age of Division, the twisted lords of the Crystal decimated the Grunok.