The 20th Anniversary Event of Blizzard's "Diablo" franchise takes you back in time to the Tristram. The original town featured in the game's first title. Players have to go into the dungeon to slay the Lord of Terror for the first or last time. As part of the Anniversary Event for "Diablo 3," players can actually get to the secret cow level and get a cow pet.

Here are the simple steps on how to get there. The first thing to do is collect the "Rotten Mushroom." The shroom is the white item dropped on level nine of the Anniversary dungeon. Step number two is to craft the "Witch's Brew" in old Tristram. Back in the old town take the first right and players will find a cauldron in an old shack. Click on the cauldron and the "Rotten Mushroom" will automatically create the "Witch's Brew."

Step number three is to revive "Farnham." To do this go in the middle of Tristram and find the dead corpse of "Farnham" in one of the burnt out buildings. After using the brew, his ghost will appear and give you an item called the "Drunkard's Debt."

From there take the item and give it to Ogden. He'll give you Garda's Letter. Give the letter to Pepin and he'll give you a "Healer's Prescription" that contains the "Schematics for a Child's Wooden Leg." Take the schematics in the real world and give it to the blacksmith. The smith will craft you "Wirt's Leg. 

Crafting Wirt's Leg costs you about one million. Once it is crafted immediately dismantle the item and you will have the Map of The Stars. Take the map back to old Tristram then look for the cows to the right of the witch's shack. Revive the cows in the order as described in the map. The order is 2, 1, and 3, corresponding to the middle, left, then right cows.

Players that have followed all the steps correctly will gain access to the secret cow level. It contains a chest that holds the "Royal Calf" pet. According to the descriptions on the event and the item, it appears getting the pet cow is the reason why the Hell Bovines went berserk.