Wither

The Wither is an undead monster, that can be created if one puts arranges four soul sand blocks into a T shape (the same way you would an Iron Golem) and then add three Wither skeleton skulls on top of it. When killed they drop a nether star, which can be used to craft a beacon. It is said that its home is in the Nether, but they mainly get made in the Overworld.

Biology
The Wither is an undead mob resembling a limbless three skulled Wither skeleton. They are also black in color, and seem to be very strong as they take a long time to kill.

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.