Wither Skeleton

Wither skeletons are black sword-wielding variants of skeletons found in nether fortresses.

Spawning
Wither skeletons spawn in nether fortresses at a light level of 7 or less. They spawn in groups containing up to five mobs.

Spawning is not limited to the nether fortresses.

On Halloween, wither skeletons have a 22.5% chance of spawning wearing a pumpkin and a 2.5% chance of spawning wearing a jack o'lantern.

Wither
On Normal difficulty or harder, the wither will spawn 3–4 wither skeletons when below half health.

Spawn eggs
A wither skeleton spawn egg can be found in the Creative inventory. This egg spawns only wither skeletons.

Drops
Wither skeletons drop:
 * 0–2 s
 * 0–1
 * 1 (2.5% chance) when killed by the player, and Looting increases the chance by 1 percentage point per level (up to 5.5% chance of a drop with Looting III).
 * 8.5% chance of dropping their stone sword, which will have a random durability, and will be always non-enchanted(may be enchanted).
 * They may spawn with armor in normal or hard, which they have 8.5% chance to drop.
 * They drop 5 experience when killed by a player or tamed wolf.

Halloween
If a wither skeleton wearing a pumpkin or jack o'lantern is killed using a tool enchanted with Looting, there will be a chance equivalent to the level of Looting used to drop the pumpkin or jack o'lantern, up to a maximum of a 3% chance of a drop.

Behavior
Wither skeletons walk aimlessly when idle, but will sprint at the player's walking speed when attacking, with their stone sword. When the player is attacked by a wither skeleton, they are inflicted with the wither effect for 10 seconds, which turns the health bar black and decreases the health by  every 2 seconds, similarly to poison. Wither skeletons deal on Easy,  on Normal and  on Hard. Like other undead mobs, wither skeletons may spawn with the ability to pick up dropped melee weapons and armor.

Immunities
Like most Nether mobs, wither skeletons are immune to fire damage, and thus are not affected by fire blocks or lava. Wither skeletons are undead mobs, causing Wither bosses to not attempt to attack them. Their immunity to fire prevents them from burning in sunlight if transported through a nether portal or manually spawned in the Overworld, but they will still seek shade and water.

Data values
Wither skeletons have entity data associated with them that contain various properties of the mob.

Trivia

 * If hit by a wither's skull, wither skeletons can be afflicted with the Wither effect.
 * Spiders and cave spiders spawned in the Nether (via spawn egg, monster spawner, etc.), have a 0.8% chance of spawning as a Wither Jockey.
 * Although they may spawn with the ability to pick up items, wither skeletons will never pick up a bow under any circumstances.
 * If a wither skeleton is wielding a bow (which can be spawned with ), it will use it like an ordinary skeleton, but the arrows it shoots will always be set on fire, regardless of enchantments.
 * Wither skeletons run from wolves like normal skeletons do.