The Secret Cow Level is actually a hidden quest. To complete it, kill The Cow King inside.

NOTE

• To open the red portal to the cow level, you have to use a Wirt's Leg (socketed or not) from the exact same difficulty.
  The recipe can be found here: http://classic.battle.net/diablo2exp/items/cube.shtml
  Being a quest item, Wirt's Leg is bound to work only in the difficulty where it spawned. A red Wirt's Leg is from another difficulty.

Anyone can enter the cow level, regardless of quest status (IIRC, it has worked like this at least since v1.10).

However, to open the portal to the cow level, the following conditions must be met,

• You have completed the Diablo/Baal quest ("Terror's End" / "Eve of Destruction") on that difficulty.
  Expansion characters must complete the Baal quest

AND

• You have NOT already got credit for killing the king.

Credit is given IF you kill him yourself, OR he dies at the hand of another player who has NEVER killed him before (meaning: it is a "quest kill"), while you are in the cow level.

NOTE: If a pre-opener (someone who has not completed the Diablo/Baal quest on said difficulty) kills the king, it does NOT affect his or anyone else's ability to open again.
NOTE: If a post-opener (someone who already killed the king for the quest in a previous game) kills the king, it does NOT affect anyone else's ability to open again.

NOTE: Being partied or not makes no difference, it only matters who actually gets the last hit (killing blow) on The Cow King.
NOTE: When The Cow King is killed by someone for the quest, he drops 8 x Stamina Potion: w00t, MILK!

This post was edited by Eywa on Apr 14 2010 09:43pm

Being partied or not makes no difference,
Sorry... but I disagree with this... in 1.09 / 1.10 / 1.11 I have encountered this to be false... and have tested it out... now maybe there might be some difference in some opinions... but it is the same as doing the "Forge" quest...

I have been level 9 and have run in group and the maker killed king... i could not make cows after that when I passed Baal... i had already been rushed to Hell A5 and started cowing in 1.09 when you could get mass levels...

I have also done above in 1.10 after being glitched to Hell difficulty... could not open cows

I have also done it similar in 1.11 Hardcore where king was killed while I was levelling from 20-25... after I passed normal baal, I could not open Normal cows.

Sorry to say this... but from actual gaming... if you are partied and one member kills the cow king (not sure of other things mentioned)... i could not make cows at all after completing baal quests in that difficulty...
___________

Edit... actually... i can test this in 1.13 now... I killed cow king in a normal cows helping 3 of my friends that were gaining levels... I will ask them to make cows in normal... (now that they have passed baal)

They were partied, they did not have baal quest... my bowazon killed king while they were sitting in town.


This post was edited by izParagonzi on Apr 14 2010 10:04pm

None of the above contradicts what I wrote. Just read it again, carefully, in context.

The quest status of the cow king slayer determines the outcome,

(1) If a pre-opener kills the king, he and everyone else would be able to open again.
(2) If a post-opener (ex-opener) kills the king, everyone else can open again.

(3) If the opener (or anyone satisfying both requirements to open the portal) kills the king, it is a QUEST KILL.

In case (3), and ONLY in case (3), EVERYONE INSIDE the cow level AT THE INSTANT THE KING IS SLAIN becomes permanently unable to create the red portal on that difficulty, regardless of Diablo/Baal quest status.


Anywhere outside the cow level should be safe with regards to not completing the quest.

Your bowazon should be unable to open again.

yep you gona miss out on low runes and gems................oh wait i once found a half assed chutas there..........

"The quest status of the cow king slayer determines the outcome,"
Ewya I think you're wrong, from my experience:
If your charecter (or your Merc's Aura!) causes any damage to the King, and a party member slays him, YOU lose the quest!
In these cases the pesron killing the King was very high level & unable to make cows himself.
I've had a couple of chars who could not cow even immediatly after they killed Baal & got to higher diff.