Lorkhan is an et'Ada. An et'Ada is translated to as an original spirit. Lorkhan is the et'Ada that is most connected to the existence of Nirn.
It was passed down that Lorkhan died, for convincing the Aedra to create Mundus*. Since he died, he didn't really have much to do with the Third Era, except for the Battle of Red Mountain, and the Amulet of Kings (those sound familiar? They should, it was Vol. 1 and 3). It is also believed that Nirn's moons are remnants of Lorkhan's body cleaved in two.
*Mundus is the plane of existence that Nirn and it's moons are located in. Mundus is surrounded by Oblivion.
Lorkhan was brought into existence by Sithis to destroy the universe. Sithis wanted this done because the Aedra had taken over everything that Sithis had made. The Dark Brotherhood supports this idea.
Lorkhan persuaded some of the other et'Ada to create Mundus. Some of the et'Ada put more time and power into the creation of Mundus. Those who put more time into it became the Eight Divines... and those who didn't became Daedra (that blew my mind). Mundus was easily changed, and the Aedra made it stronger in some ways and weaker in others. Once Mundus was completed, Mangus, the main architect began to doubt the creation of it. There was a convention held to discuss it.
At the convention, it was decided that Lorkhan would be punished for being a bad boy and convincing the Aedra to be a part of making Mundus. He battled Akatosh and was killed in the fight. His divine power and heart was thrown into Tamriel and the rest of the Aedra moved away.
Lorkhan is one of two et'Ada to be in all mythology on Nirn. Along with Akatosh. Opinions of him vary from some races to others. The mer see him as an enemy, yet men see him as a hero. In Cyrodil, he is called The Missing God, because he died. Rip.
His heart was hidden in Red Mountain. I don't really need to go to much into what happened there. That was my first lore post. But his heart was in the mountain, the Dwemer were trying to make their own god with it and the Chimer didn't agree with that. The tribunal got into the mountain and struck the heart with enchanted tools and the Dwemer disappeared.
This is not known if completely true, but Mankar Camoran said that Lorkhan made Tamriel, and that it was a plane of Oblivion for Mehrunes Dagon. Lorkhan didn't want that to happen because he loved Tamriel. That would explain why the Oblivion crisis happened. Lorkhan was dead, so there was nothing stopping him from re-taking Tamriel.
That's it for this week's volume of Life Magazine. Wait, I mean my lore post. I hope y'all liked it and learned some stuff about lore...Lorekhan (minus the "e").