Wither skeletons are a variant of regular skeletons found only in nether fortresses. They are tall and black in appearance and are equipped with a stone sword that inflicts a poison-like wither effect. They are also the only source of wither skulls.
A wither skeleton in a nether fortress (Via Screenshots)
Wither Skeletons only spawn in nether fortresses at any light level between 0 and 11 usually in groups of 4. Since they are immune to the damaging effects of wither roses, they can spawn on them.
On Halloween wither skeletons can spawn near carved pumpkins (22.5% chance) and may sometimes spawn wearing a jack o’lantern (2.5% Chance). This only happens in Java Edition.
A wither will spawn 3-4 wither skeletons once below half health on normal and hard difficulties. This will only happen in Bedrock Edition.
When idle, wither skeletons like to space out and roam around aimlessly, but will attack players, piglins, piglin brutes, iron golems, snow golems, and baby turtles on sight. When a wither skeleton attacks a player/mob they inflict the wither effect which lasts for ten seconds in all difficulties, they turn the health bar black, and your health is reduced by 1 heart every 2 seconds. It works similar to poison but it will kill you, unlike poison which leaves you at 1 or half a heart.
In normal and hard difficulties, some wither skeletons may pick up dropped gear. They can even pick up swords higher than stone tier, and any type of armor.
When a wither skeleton is in the Overworld they will seek shade or water even though they don't burn in sunlight. Like most undead mobs, they sink in water but can drown, get healed by instant damage, and are harmed by instant health effects. They are also immune to poison and regeneration effects. Players can burn them by launching a trident with the channeling enchantment at them during a thunderstorm but this can only be done in Bedrock Edition. Wither skeletons will avoid wolves and flee but will attack back if aggravated.
Wither effect on the player's health (Via Screenshot)
It's recommended to kill them from afar with a bow and arrow, but if close-range combat cannot be avoided, then it is imperative that you use a shield to block the wither skeleton’s attacks as the wither effect can be deadly. If you are desperate, then running inside a space that is only two blocks high will guarantee safety, as wither skeletons are taller than regular skeletons and can’t chase after you.
A wither unable to pass through a gap two blocks high (Via Screenshot)
When killed, a wither skeleton will drop 5 experience orbs and 0-2 bones, the maximum number of which can be increased by 1 per level of looting. If the wither skeleton was equipped with any armor they will drop between 1 and 3 extra experience orbs per piece of armor. They can also drop their unenchanted sword with random durability which has an 8.5% drop rate.
The odds for this can be increased to 11.5% with the Looting III enchantment. When killed by a player or a tamed wolf they have a 2.5% chance of dropping a wither skeleton skull, this drop rate can also be increased with the help of the looting enchantment which will increase it by 1% or 2% per level of looting of 5.5% or 8.5% for Java and Bedrock Editions respectively.
Wither skeletons were added to Minecraft back in v1.4.2. They received minor changes to how they behave when idle or around other mobs till v.1.14 when their textures were reworked and completely changed, along with them becoming immune to the wither effect. To this day they are the only mob that can spawn on wither roses.
Wither skeletons are a formidable enemy to encounter in nether fortresses as their attacks are very dangerous. Their presence at fortresses makes the game more challenging and immersive. These are tough enemies that will test you whenever you encounter them so you shouldn't let your guard down.
A. Their biggest weakness is the inability to walk through a passage that is two blocks high, much like endermen.
A. The wither effect will do 5, 8, and 12 damage in Easy, Normal, and Hard difficulties respectively.
A. Yes, when a normal skeleton is struck by lightning it will turn into a wither skeleton.