You need to make a 3x3 square of netherrack, a zombie head in the middle. (which you can get from Sapphire Dungeons) Then light the fire and then you get the chance to run away.
When spawned, a Zombie will appear with the Charged Creeper glow, it will get bigger and bigger until it looks like a Bigger Giant
When he is big, he looks like a huge zombie you can only hit in the legs.
He will attack you by grabbing you, if you get grabbed you will lose 5 hearts and fall back to the ground (which you will lose 2 hearts)
If he punchs you, you lose 4 hearts.
He can spawn Zombies and Baby Zombies, but it fails in day.
10 HP left
When the boss is down to 10 HP, he will be shrunk to a zombie with the charged Creeper effect again, he is healing then, if you kill him he will turn big and then explode. (the explosion is only the size of 10 TNTs.)
You ready? - Get a Zombie Head
BIG ZOMBIE! - Spawn in the Giant Zombie
Hmph... Didn't try - Kill the Giant Zombie
The creator of this mod loves Giants, so he made a boss for him! :D
If you add a sapphire block into the middle, he will wear a sapphire helmet! Giving him 110 hearts, no protection though. He will drop the helmet
Added Giant Zombie BOSS and Sapphire Helmet version.
Turned the Giant Zombie BOSS bigger, so it doesn't look like a Giant.