“Wither Skeletons are dangerous hostile mobs that spawn in Nether fortresses. Wither skeletons are the Nether equivalent of skeletons. Wither skeletons are three blocks tall, use stone swords and, like other Nether mobs, are immune to fire. When attacked by a wither skeleton, the player is inflicted with the Wither effect for 10 seconds, which darkens the health bar and gradually damages the player over time.”
Wither Skeletons only spawn in or near Nether Fortresses at light levels of 7 or less.
Wither Skeletons are, like all Nether creatures, immune to fire. When they hit you, you will get the Wither effect for 10 seconds, darkening your health bar (meaning you won’t be able to see how much health you have left) and gradually damaging you, similar to the Poison effect.
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