Minecraft Wither Skeleton

Minecraft wither skeleton: fortresses, skulls and coal

The wither skeleton is the tall, black variant of the skeleton, armed with a stone sword instead of a bow. It only spawns in Nether fortresses, at light level 0 to 7, in groups of 5 in Java and 2 or 3 in Bedrock. Inside each fortress piece it can spawn on any block, but across the rest of the structure's area only on nether bricks. It is the only mob that can spawn inside wither roses, since their effect does nothing to it.

Its hit applies Wither for 10 seconds: your health bar turns black and you lose one point every two seconds. Unlike poison, it can kill you. It runs at players, iron golems, baby turtles, piglins and piglin brutes within 16 blocks. It is immune to fire and to Wither, and although it does not burn in sunlight, in the Overworld it still looks for shade during the day.

It stands about 2.4 blocks tall, so it cannot fit through two-block-high gaps. That is the usual way to stay safe in a fortress: leave corridors or shelters two blocks high where it cannot follow. Wolves attack it, and in Java it runs from them.

It is the only source of wither skeleton skulls, three of which summon the Wither, and the only renewable source of coal. It can also drop its stone sword, with an 8.5% chance, and gives 6 to 8 experience when it does not. The Wither itself summons 3 to 4 of them when it drops below half health on Normal and Hard.

Sources: minecraft.wiki/Wither Skeleton