Zombies are everywhere in Minecraft. It is likely that they are the hostile mob you will encounter the most in dark tunnels and when walking around outside at night time or in the rain. Zombies have such an impact on the game that they also can affect and take over Villages. Here is how you can create or cure Zombie Villagers in Minecraft.
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The difference between a normal Zombie and a Zombie Villager can be seen in their face. If they have the Villager face, they can be transformed back into a normal Villager.
To create a Zombie Villager, a Zombie must attack a Villager either in Normal or Hard difficulty; it is impossible on Easy. There is a 50% chance on Normal and a guaranteed transformation on Hard whenever the Zombie hits the Villager. The best way to do this is to go to a Village at night time and break the wooden door on a home with Villagers inside.
If you do not want to unleash Zombies on Villagers, there is a 5% chance that a Zombie Villager variant will spawn in the wild when a normal Zombie spawns. There is also a 2% chance that a Village will generate as an Abandoned Village and be filled with Zombie Villagers.
To cure a Zombie Villager in Minecraft, you will need a Splash Potion of Weakness and a Golden Apple. To make a Golden Apple, you will need to craft it using an Apple and eight Gold Ingots. For the crafting recipe, place the Apple in the middle slot with the Gold Ingots surrounding it.
When you have your items, find a Zombie Villager and trap it somewhere out of the sunlight, or it will catch on fire and die. Throw your Splash Potion of Weakness at it. If you hit it, you will see some gray swirls coming up from it, showing it is affected by Weakness. Before that effect drops, pull out the Golden Apple and give it to them. The swirls will turn red, and they will transform into a Villager in about a minute or two.
It takes a bit of waiting, but once the transformation is complete, you have another Villager to trade with and earn the Zombie Doctor achievement.