You can still re-visit the Secret Cow Level in the current difficulty, but someone else will need to open the portal for you.Whether or not you are in a party does not matter, if you are inside the Secret Cow Level when the Cow King dies, you will receive credit.Whenever the Cow King dies, anyone currently inside the Secret Cow Level will receive credit for the quest, and be unable to open the portal to the level again in the current difficulty. In Diablo 2 and Lord of Destruction, a hidden quest tracks whether or not you have defeated the Cow King in the current difficulty. It can be hard to distingush the King in a crowd of other cows, but he is always Lightning Enchanted. The Secret Cow Level always contains a single super-unique monster, the Cow King.
Somewhere inside is a wooden "fort" with higher walls, open corners, and the Cow King. Hell Bovines densely populate the whole zone. It resembles Blood Moor but with wide-open spaces and the occasional wooden fencing. The area is a single outdoor zone, with no sub-levels or dungeons. The number of scrolls inside the Tome does not matter and it will not affect the "quality" of your portal or loot.The Leg you use must have been obtained on the current difficulty, Legs from other difficulties will not work. Wirt's Leg can always be re-obtained from his body in Tristram.This restriction does not apply in Diablo 2: Resurrected. Someone else must open the portal for you. Diablo 2 / Lord of Destruction: If you have been previously present in the Secret Cow Level when the Cow King was slain, you will be unable to craft this recipe yourself in the current difficulty.
While standing in the Rogue Encampment in Act 1, combine a Wirt's Leg + Tome of Town Portal in the Horadric Cube.
Expansion characters must have killed Baal, while classic characters must have killed Diablo. In order to open the portal to the Secret Cow Level, you must first finish the current difficulty.