A large variety of Skeleton and Skeleton Archers, Burning Dead, Corpse Bows, and Skeleton King Leoric
Undead Crown from Skeleton King Leoric, additional magic items from the secret room opened by hitting the four crosses in Leoric's lair
This quest is different in the single-player game than in the multiplayer game. Ogden will initiate this quest, which, like the Poisoned Water quest, also occurs in a separate mini-level, this time off level three. There is a separate entrance to the Skeleton King's Lair that can be found by moving the mouse over any staircases you encounter on level three. Once in his lair, take it slowly and gradually pick off his skeleton army (without getting too many of them on the screen at once) to avoid being overwhelmed. Use Holy Bolt as much as you can. If you engage in hand-to-hand combat, try to use a blunt weapon, like a club, mace, or staff, instead of a cutting weapon, like a sword. You may meet your first skeleton archers on this quest. Avoid advancing too far into a room to avoid being caught in a crossfire.
The Skeleton King is straight left. Look for the glow he creates. As with the Butcher, Stone Curse is once again the easiest way to defeat your enemy - cast it when he gets close and attack him while he's vulnerable. Holy Bolt spells also work very well against the Skeleton King. It's probably not wise to fight him hand-to-hand unless you have a high dexterity, a Bear weapon, or an item which allows you to fast attack or fast recovery. If he gets near you, you can run away from him (he may chase you for a while but will eventually veer off). He also has the nasty habit of raising the skeletons you've already killed, so try to take him out quickly.
Once you've killed him, pick up his Undead Crown (a great item for fighters), and don't forget to click on the crosses in each of the corners - they'll open up a secret room with more magic items.
A large variety of Skeleton and Skeleton Archers, Burning Dead, Corpse Bows, and Skeleton King Leoric
Undead Crown from Skeleton King Leoric, additional magic items from the secret room opened by hitting the four crosses in Leoric's lair