Son of Odin, Prince of Asgard, and God of Thunder, Thor uses his mighty hammer Mjolnir to protect the people of Midgard!
After Thor's adventure on Earth, aka Midgard, the thunder god felt a need to protect the place and its people. Joining the Avengers allowed him to do that. So when the realm came under threat from the power of the Infinity Gauntlet, Thor was among the first to answer Agent Coulson's call to stop the threat.
Thor was surprised, however, to find that the threat came from fellow Avenger Sam Wilson, the Falcon. Thor tried to convince Sam to listen to Captain America, but failed in his efforts, and the Earth was subject to the power of the Infinity Stones.
Thor returned to Asgard to deal with the fallout of Sam's snap, but was summoned back shortly by Nick Fury to aid in the Secret War. However, he was none too happy to discover that Fury had been meddling with the Tesseract. Before he and Fury came to blows, Hela, goddess of Death, arrived.
Thor, Heimdall, and Lady Sif fought valiantly, but ultimately fell to Hela's wrath. She spared the three Asgardians, as their souls were bound for Valhalla, and no use to her, but turned her attention to Fury and Coulson. Before she finished them off, Nick Fury blasted her with a Destroyer Rifle. Hela left, but vowed that this was not the end, and after she took Midgard, Asgard would fall as well.