Tips for keeping your ability to make the Secret Cow Level: Some good detail can be had at Diablo's official D2:LOD site, The Arreat Summit, at. You may ONLY do this if you have not killed the Cow King on that difficulty before (normal, nightmare, hell), and not been partied with someone who got the killing blow after you got a hit in on the king. Back in the Rogue Encampment transmute the leg and a tome of town portal in your horadric cube to create the red portal leading to the Secret Cow Level. This is the 'Rescue Deckard Cain' quest.) In the upper left corner of Tristram is Wirt's body. (You must have retrieved the scroll of Inifuss from Dark Wood, talked to Akara, and touched the 5 stones in the correct order to open the portal. A Wirt's leg can be acquired from Tristram, which is accessed by the red portal in Stony Field. After killing Baal (D2:LOD expansion) or Diablo (D2 classic) in each difficulty (normal, nightmare, hell) you may then create the cow level in that difficulty. You be the judge on whether or not the grammar is adequate.

Many of the comments here have incorrect information on the cow level, and the one that does give the correct info has terrible grammar.

Diablo 2 classic secret cow level