In a hidden Inhuman city, he was known as The Healer.
Thane's true nature was revealed when Black Bolt activated the Terrigen Bomb during his fight with Thanos, leading to wide-spread mutations across Earth. However, as this happened his people were killed in the process, due to his powers.
Thane was created by Jonathan Hickman and Mike Deodato Jr. in New Avengers #10, as part of the Infinity crossover event.
After his powers were awakened by the Terrigen Bomb, Thane, who had spent his life healing others, looked in horror as his new power had killed all he knew. He was found by Ebony Maw, who quickly manipulated and trapped Thane, who is the last remaining offspring of Thanos.
As Thanos was finally going to kill his last child, the Avengers arrived on the scene. Ebony Maw continued to talk to Thane about his power and destiny. He released Thane to see if he would save the world, in doing so become his father's son and take life. Thane accepted and put Thanos in a state of 'living death.'
He left the Earth with Ebony Maw, still under his manipulation.
Powers & Abilities
After being exposed to the Terrigen Bomb, Thane possesses the power of death. He is truly the son of Thanos. With his left hand, Thane causes death. With his right, Thane can encase beings in a state of living death.
Thane also possesses superhuman strength.
As part of the Special Ops assignment, Infinity (13), a character by the name (Modern) Thane teams up with your agent for a Mini-Boss battle in Mission 3 - The Search for Thane.
"The hunt is on for the mysterious Thane. Whoever he is, Thanos wants him... which means we have to do everything in our power to keep Thane out of his hands." - Avengers Alliance