1.11 version over here : https://minecraftcommand.science/commands/44434
With this tool, you will be able to turn parts of the overworld into nether.
First you will need to create a nether sacrifice altar (from bottom to top: a 3x3 obsidian platform, a block of obsidian in the center, fire)
Stand on the fire for 2.5 seconds in order to get a nether core spawn egg. Your resistance and fire resistance effects will be removed, so you WILL take fire damage :P
When you place the nether core, he will die instantly, after turning a 21x21x21 region into nether blocks (sand=soul sand, grass=netherrack, etc...)
The nether core will burn pigs, cows and sheeps, turn zombies into pigmen and skellies into wither skellies.
Video about it here : https://www.youtube.com/watch?v=BA2uLNXcGco (it's in french but you have the image at least :P)