Thal'Nath is a demon of considerable strength. He was one of the original demons that Sargeras took control of and locked in a corner of the universe.
He was kept secret by Sargeras and was taken in as a special apprentice, unknown to any but Sargeras. When Thal'Nath disobeyed an order to release some of his power, Sargeras imprisoned him in the center of Azeroth. He was linked to the world through special shards contained in a cavity deep within the earth. The closest link to this cavity is beneath the Stormwind Stockades. Thal'Nath can still communicate with those in Azeroth, but in order to make any minor changes to a person they must be inside the stockades.
Potential as a Demon Edit
Because he was imprisoned for so long, he no longer has a lust for power. He currently is trying to escape his prison so he may be free to leave Azeroth once and for all. He chose to enact his plans after the defeat of the avatar of Sargeras.
Current Situation Edit
Thal'Nath plagued the mind of a young Draenei, Orshanai, to try and get her to understand him. He eventually was able to win her over and she worked to establish a link between him and her mind. Through a ritual, he could be summoned into her mind and he could control her body to some extent. After meeting with Sulphuras of Broken Pact, he allied himself with her cause and is now able to summon himself freely into Orshanai's body using an enchanted black rose. He has promised to help Sulphuras in her quests in return for her support to free him from his prison.