8. The Cow King - Diablo 2
The first but not last bovine-related enemy on this list, The Cow King has come to occupy a soft spot in the hearts of many video game fans in the decades since Diablo 2 launched.
A secret boss inside a secret level, in order to find the Cow King you first have to find the secret cow level inside the RPG. This hidden environment does exactly what it says on the tin: transports players to a big field full of demonic cows eager to rip and tear your flesh.
Known as Hell Bovines, these not-so-cuddly creatures will mess your day up, and the king of these can be found as you venture further into the level.
The Cow King might be the most well known hidden enemy on this list today, but back when Diablo 2 first dropped his existence was a complete surprise to the players who stumbled across him.