Eric Masterson assisted a wounded Thor, picking up Mjolnir (proving worthy) to help him. Later he was injured taking a blast meant for Thor. Thor later bonded himself to Masterson, with the permission of Odin, to save Eric's life.
When Thor killed Loki, Odin punished him and had Masterson replace him as Thor. Eric was uneasy in the role, finding it difficult to convince his teammates that he was the same Thor that had accompanied them on previous missions. He eventually admitted the truth. When Thor returned, Odin had the mace Thunderstrike given to Eric. He continued to adventure, calling himself Thunderstrike after the mace he used.
He and James Rhodes acted as Secret Defenders assisting the Silver Surfer.
Thunderstrike was confronted by a new Bloodaxe, who claimed the wielder was someone close to him. It turned out to be his girlfriend, Jackie Lucas. Eric was able to save her and use both his mace and the Bloodaxe (Enchanted Axe) to battle Seth, becoming possessed in the process. He died to purge himself of its corruption and refused a place in Valhalla.
Thunderstrike would later appear (complete with mace) in Avengers Vol. 3 #10 & #11 as an undead Avenger minion of the Grim Reaper. After overcoming the Grim Reaper's control, he (and other undead Avengers) were returned to the spirit world by the Scarlet Witch. It is not made clear if this was Eric that returned, or a magical construct of some sort, although his last words were to Thor in regards to checking on his son Kevin.