This mod is for Minecraft 1.12. It allows you to summon a blue wither skull, which has the ability to destroy obsidian.
You just need to add "powered:true" to the dataTag section of the /summon command.
The below command is an example of how to shoot a blue wither skull downward.
/summon wither_skull ~ ~-1 ~ {direction:[0.0,-0.2,0.0],power:[0.0,-0.1,0.0],powered:true}


To install the mod follow these instructions:
1) Copy the 1.12_Blue_Wither_Skull_Mod folder to your Minecraft "versions" folder. The needed json file is already in it.
2) Copy your 1.12.jar file into the 1.12_Blue_Wither_Skull_Mod folder, and rename it to 1.12_Blue_Wither_Skull_Mod.jar
3) Remove MOJANGCS.RSA and/or MOJANGCS.SF from the jar's META-INF folder. Alternatively you can remove the entire META-INF folder.
4) Extract the contents of modfiles.zip, and insert them into 1.12_Blue_Wither_Skull_Mod.jar