Whimsyshire is to Diablo III what the Cow Level was to Diablo II. This is perhaps the Blizzard developers having some fun with the fact that earlier in development people were calling the game “too bright”. It also fits the theme of the t-shirts Blizzard began selling some time back.
This guide will walk you through the steps in acquiring all of the items for the Staff of Herding, which is the pre-requisite to enter Whimsyshire. Unlike Diablo II where you had to gather the items each time, you only have to make the staff once. It can be upgraded 3 times at an incrementally higher cost (250k for Nightmare, 500k for Hell, 1 million for Inferno) to enter the level at each of the difficulties. Gorell the Quartermaster located in Bastion’s Keep Stronghold during Act 4 sells the Nightmare, Hell and Inferno plans for 1 gold. Once upgraded, the staff can retroactively be used to enter Whimsyshire at lower difficulties.
Leoric’s Shinbone spawns randomly in the fireplace of Leoric’s Manor near the end of Act 1. It’s always in the room on your first right (if you were entering from the courtyard). If you Start from the beginning of the quest The Imprisoned Angel you can take the waypoint to Leoric’s Manor and it’s just a matter of running inside, killing a few mobs and checking for it. The fireplace should have some Burnt Logs which you can click, doing so will give you the shinbone. If it’s not there, leave the game and resume and you will be right at the door of the Manor again.