Cow Mage and Vengeful Bovi

Description: When a player kills 20 cows the 20th cow will drop a map that takes the player to the lair of the Cow Mage. When found a boss bar will appear and the Cow Mage will appear. Abilities of the Cow Mage are summoning Vengeful Bovi (a cow which is basically a zombie cow), charging the player creating intense knock back, and a rotting cloud which gives the player wither and hunger effect.

Hostility: Hostile 

Drops: Staff of the pasture (summons Vengeful Bovis which do your bidding)

Spawns: Unknown

Notes: If you're curious why I got the name Bovi is that it didn't feel right to call it a zombie cow, and doing some research the name Bovi comes from the family called Bovidae, the family where cows come from.