The mad King Leoric - Boss in Diablo 3?

Leoric the Skeleton King returns in Diablo 3! His undead bones have been reanimated, and once again he's raised an army of the undead and awaits any hero who might dare bring the warmth of life into his tomb, in the catacombs beneath Tristram. Leoric is one of the first quest bosses a new character encounters, and defeating him brought an end to the Blizzcon demo, the first playable version of Diablo III ever seen by the public.  
 
Leoric is found on a throne at the end of a scripted level. The player must fight through several blockades and traps to reach Leoric's room. Along the way, Leoric's ghostly form is encountered, during which he taunts you before blowing back through the floor and vanishing, just as a great number of undead emerge from all sides of a large room. 

Once you do reach Leoric's throne, a bridge crumbles behind you leaving no escape; you must defeat Leoric to survive. Leoric's giant bones are found on a throne, and they remain motionless until a player produces The Crown of the Skeleton King, a quest item found in the dungeon above. The crown restores Leoric to life, and he rises up, taunting the player wielding a massive two-handed maul. As soon as Leoric is activated squads of all types of skeletons come from the sides of the screen, and more are found throughout Leoric's throne room, if the player retreats from the dais on which Leoric's throne sits. 

Leoric deals substantial damage with his massive club, but only swings once every few seconds, giving a player plenty of time to score hits on him between swings. It's a good idea to try to stay just out of range so you can dodge the attack, since it deals considerable damage. 

He also retains his ability to summon skeletons, and will do so during the fight, if given the opportunity. Most players at Blizzcon would fight Leoric for a moment, then run off and kill some of the skeletons he summoned to get a health globe or two, then return to the battle with Leoric. 

Leoric dropped 4-6 rare items when killed in the Blizzcon build. We can`t predict how valuable he`ll be in the final game yet, because Diablo 3 is far from completion.