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. When killed it drops a nether star you can use it to bring the ender dragon back to life after death, it is said that its home is in the nether but it mainly get made in the overworld or 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.