After only 3 years of sitting on the throne, he was killed by it.
The chronicle says that he was crushed by the throne's canopy that collapsed on top of him, and succumbed to his wounds soon after. Some people at the time (and since) theorized that it was a failed assassination attempt that was finished up a couple of days later, probably by poison. Or maybe just a freak accident? Hard to tell after almost a thousand years. Definitely an unusual way to go.