1) Summons in a Wither Minion every 7.5 seconds.
2) Summons a Wither Bomb below it every 15 seconds.
3) Has 8 Shields around it, blocking Arrows near it. (You can still shoot the Wither Storm, it just takes precision.)
4) Covers the ground near it the Netherrack, making fire stay lit.
5) Lag. Lots and LOTS of Lag.
Once the Wither Storm is defeated, it'll drop an item called "The Warrior's Sword". It can't be destroyed by Lava, Fire, Cacti, or pretty much anything. When on the ground, It'll give everything in a 5 block radius Regeneration. The Sword is also powerful as heck
30,824 characters (It's more compact, but still works the same!)
-Vanilla 1.8.8 for Singleplayer and Multiplayer
-10 hours of work
Crafting Recipe (Drop Items 1, 2, and 3 on the ground to craft Item 4):
4 Wither Skullls + 5 Soul Sand + 1 Beacon = Wither Storm Base Template
The Base Template is an easy way of creating the structure required to spawn in the Wither Storm. Alternatively, you can build the structure yourself: