Quote from Bernardos
Cheat yourself a Vorpal II enchantment. I'd justify it easily in your situation.
1: Hit escape, create LAN world, allow cheats: on. Already have cheats on? Skip to part 2.
2: Press 'T', enter the command: "Gamemode 1" (creative)
3: Give yourself whatever tools you need to create an enchantment room. Or if you already have one, give yourself a sword of your choice and enchant it. If you don't get Vorpal on it, trash it and try again. Afterwards, I don't know if you need to manually change back to gamemode 0 (survival) or if it's enough to just log in and out. At least doing that disables the LAN world, so you will probably have to do it anyway.
Maybe there are easier ways to doing this, but that's how I do it whenever the coding decides to screw me over or/and treat me unfairly.
1. Have NEI installed. (Cheat mode on, of course.)
2. Open inventory.
3. Press X.
4. Place sword.
5. Choose '2' with the arrows.
6. Click 'Vorpal II' on the right.
7. Drag sword to inventory.