The cows in this level aren't immune to anything, even on Hell difficulty. What this level is good for is insane mob density If you are looking to farm Champ/Boss packs there will definitely be better areas for you to go. The Fortress that the Cow King is in looks like this on the map. In the screenshot further down you can see what that building looks like ingame it's basically large log walls with corpses on pikes throughout. The Cow King will always spawn inside or out front of this building with a few groups of cows to accompany him. When looking at the map keep an eye out for the structure shown in the screenshot below. Thankfully you can easily identify where the Cow King is on each map so you know to avoid him. Unless you are playing on 1.13 with PlugY or on some Diablo 2 Mod that allows you to repeat the Secret Cow Level you're stuck with this really stupid quirk. **IMPORTANT** Don't kill the Cow King in the Secret Cow Level on the 1.14 version of the game or you can not open the portal again on that difficulty on that character. So important we're gonna make it stand out all big and stuff. There is one more thing worth mentioning too that is extremely important. I'm not entirely sure what causes this bug but I have had it happen enough times on enough characters that it is worth mentioning. Or complete a quest in the next difficulty then come back to the difficulty you beat the game on and try again. It isn't uncommon for the combine to fail sometimes, usually you have to log fully out of the game then back in if this happens to you. Wirt's Leg + Tome of Town Portal = Secret Cow Level Once you've done this you'll need to combine Wirt's Leg in a Tome of Town Portal in the Rogue Encampment to open the portal to The Secret Cow Level. When you are logging back in make sure you choose the same difficulty that you beat the game on. In order to reach this level you will need to complete the game (defeat Baal) and log out or take the Destruction's End portal so you see the screen with Deckard Cain.

Secret Cow Level is one of the most famous areas in all of Diablo 2 and is a bit of a meme in Blizzard games. Hell Immunities: None (Only Boss/Champ packs)

How to Reach: Rogue Encampment > The Secret Cow Level Secret Cow Level Farming Location - Diablo 2

Diablo 2 get to secret cow level