You fight your way through a horde of Seekers and Lurkers in the puzzles to get to Miraak. Then, you engage in an epic deathmatch with the only other dragonborn other than you. After probably a half hour or so of contstant pausing to heal or hiding behind rocks and shooting him from afar, you finally manage to kill him. After you exit Hermaeus Mora's realm, you feel powerful. Like you could do anything. So what do you do? You attack the thing nearest to you.

So, you charge at the Netch, weapon drawn and attack it. A few minutes later, you enter a loading screen. The Netch killed you.