Udder Cowlamity

Udder Cowlamity is an in Diablo III, only available in March. It only occurs in Adventure Mode.

To start it, one needs to get into Ruins of Sescheron, enter the Elder Sanctum, find Immortal Throne and approach the throne itself. On the way, huge braziers will light as the Nephalem steps close, and the chasm beneath the throne will ignite and burn brightly. As Kanai is approached, he will awaken, his spirit getting out of the body, and open a red portal, entering it shortly and inviting the hero to join him without saying a word.

The event starts upon entering the portal to Kanai's Stomping Grounds. The goal is to kill every single Infernal Bovine on the map, with King Kanai slightly helping in battle (he is essential NPC, and therefore cannot be harmed). A few Elites will be found across the forest, but no Unique Monsters.

Killing them all awards gold and experience, opening the portal back to Elder Sanctum. Upon departure, King Kanai will silently thank the player, disappear and re-enter his body to rest again.

If the month is any other than March, the event will not happen, and there will be no interaction with King Kanai.

Trivia

 * This whole event is a homage to Kevin Griffith (better known as Kanai), who was born in March. The traces of Secret Cow Level are also noticeable, though Not The Cow Level may be more expressive on the bovine theme.