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 hints were dropped, adding more fuel to the fire. It's not much to go on, but 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.
