==The "Not the Cow" level==
For In Diablo III, for a limited time from dawn on May 15 to dusk on May 21, 2015 there was a chance to encounter a Herald to the Queen, which, when killed, left an opened portal through which player(s) could enter the secret level. It could only be opened once per game, and once inside, there was no Obelisk or portal back (except for the entry portal). However, the portal stayed open for the rest of the game, even after the zone was fully cleared.
The zone was always based on the Fields of Misery, but it could be opened from any map on any difficulty level in either Campaign or Adventure mode.