5. Malthael

Malthael after his transformation to the Angel of Death.

The last boss of the franchise is Malthael, the Angel of Death. Well he was the Angel of Wisdom, but death sounded cooler I guess. He decided that there is only freedom and hope in death, and so everything and everyone has to die. That is the short version of his story.

This guy was unusually tough compared to the other bosses in the game. Add to the fact that most players played the game on expert difficulty or higher since they got an experience boost from it, and Malthael was nearly unbeatable. It sounds silly, but it was humiliating to have to drop the difficulty back down to normal in order to beat this guy when I could beat all the other bosses on master difficulty. 

The Malthael fight has several phases that make him untouchable. He gets a force field around him that kills you very quikly if it touches you. When the second phase of the fight begins, Malthael will start shooting out red fire all over the map. It will kill you if it hits you and so you have to hide in the only one spot avaliable on the map.