Tey'talia was once a gaia class world before the Tey'talian civil wars started this world was once beautiful one of the most beautiful worlds, and when the wars started this world became more toxic due to the chemical and bio weapons being used. The Tey'talians were once a more human appearing race but due to the toxicity they evolved and mutated into the current Tey'talians now, they look more menacing and demonic. The torturing didn't help them using the same bio and chemical weapons that formed them into them they have to become immune.
Tey'talia is one of the most toxic worlds in the galaxy currently. However this world isn't good for travelling they have to detox and humans and humanoids must wear biosuits to survive the harsh atmosphere the Tey'talians have become aquainted to breathe.