Invincibility
Use Notepad to edit " \Scripts\Default\Gamerules.lua" file ( make a backup first!). Find the following line:
ai_to_player_damage = { 1, 1, 1, 0.5, 0.5, 0.5 }
and change it to:
ai_to_player_damage = { 0, 0, 0, 0, 0, 0 }
Save the changes, and run the game.