Wither

The Wither is a boss in minecraft they only way it can spawn if you put 3 wither skeleton heads on soul sand make it in a shape of a man, then it comes to life (although it's technically not alive). When killed it drops a nether star, which can be used to craft a beacon. It is said that its home is in the Nether, but it mainly gets made in the Overworld, the End or Nether.

Biology
The Wither is an undead mob resembling a limbless three skulled Wither skeleton.

Society and Culture
While they don't appear to have an actual culture, they seem to be very nihilistic, as they attack and kill anything they see.

Notable individuals
Most individuals are destroyed after their creation.