To get this quest you talk to the injured villager.(after killing the zombies eating on him) Then you get the quest and the quest thingy says
"Descend into the catacombs and destroy the arisen Skeleton King and his army of the undead"
Then you go into the Tristram cathedral and slaughter some monsters and stuff, then there is a room where there are four huge pillars that doesn´t do anything when you go to approximately the middle of the room the skeleton kings ghost pops up and says "You dare bring the warmth of life into my tomb!!?? Prepare yourself mortal to serve me for all eternity!!!!" then he puts his hands up and a glow in them starts then the four pillars starts a blue fire on the tops of them. apparently the player(s) are supposed to destroy the pillars,at the same time there are skelly´s going to attack the player(s). So when the players destroy the pillars they apparently get out of the room or something(or like the skelly´s stop coming maybe)and then the players can continue their quest to kill the skelly king. The next area you see him in is where his corpse is,you are supposed to drop his crown there, if you drop the crown his ghost comes flying and goes into his corpse and reincarnates him. Then he stands up laughs a loud"HA HA HA!!!" and goes after the player(s) at the same time skelly´s come from the sides of the room to try to assist their master but(most oftenly)they fail and the player(s) kill the skelly King and completes the quest.