The search for the Diablo 4 cow level is much more than a cowspiracy (apologies) at this point. IGN spoke to the game's production developer Tiffany Wat, and associate game director Joe Piepiora at BlizzCon 2023 where [[link]] hints were dropped, adding more fuel to the fire. It's not much to go on, but [[link]] Wat may have hinted that players are heading in the right direction: "I will say, however, if people have picked up any items from their cow campaigns… cow slay-age campaign… they should hang on to them."
The items Wat is likely referring to are the Bloody Wooden Shard, Musky Tome, and Metallic Fragment. You need to slay three sets of 666 cows, with your final kill being in distinct regions. Each set of cattle slaughter will end in a relic being dropped, which prompts a key to be dropped when used in Ken Bardu. The key is for Forlorn Hovel where you'll find 28 cows. Killing those cows drops some stamina potions (a reference to when you kill the Cow King in Diablo 2 and he drops stamina potions). This seems to be where the search has halted for now.
There has been much development since Diablo general manager Rod Fergusson said the team had [[link]] been "really focused on trying to keep it as grounded as possible" in an interview with Kinda Funny back in May, adding that " because of that, there is no secret level in Diablo 4 that people might be looking for." Since then though, hope for the bovine secret grows stronger with each discovery.
There's more than just the potential of a cow level to come. The Vessel of Hatred announcement was made at BlizzCon 2023 and it looks like the expansion will be a throwback to Diablo 2, with a brand new class, coming in late 2024.