Quote from xQuencher
Here's my idea:
There will be a enlargened statue of a Wither inside a Nether Fortress, in a random location. You will need to place 4 redstone torches around the statue to activate it. Once activated, the statue will glow a hyper-charged-creeper-glow and its health will increase. When at max, the statue comes to life and starts attacking. The same attacks the Wither has currently could be unchanged during the battle, they're pretty good. Once you get its health down to half way, the Wither will move slower but fire stronger attacks (is this already implemented?). When you finally kill it, you will recieve a Wither Sword. This sword has the same durability as a Diamond Sword and the same texture, but it is purple and black and poisons the enemy when you hit something with it. A sprint attack with this sword would cause a shockwave effecting all nearby enemies (10 blocks, maybe?)- damaging and poisoning any within 5 blocks a bit and poisoning the rest.
There's this thing called a "period", you should consider using it
The way of implementing the Wither has already been decided. Not much to say any more.