You don't need to be invulnerable to enjoy the game. There are also spells you learn that allow you to heal yourself.
But, just because they disabled cheats doesn't mean it's impossible.
I just found this: http://forum.cheatengine.org/viewtopic.php?t=568485&postdays=0&postorder=asc&start=30
It's a trainer.
A trainer doesn't modify the game files, it modifies the game in memory while running allowing you to do things even if the game has disabled them.
Disclaimer: Trainers often show up as viruses in scans because they modify running programs. Proceed at your own risk. I'm not responsible if it breaks your computer. I have not tried it.
From what I can tell, the trainer has different parts. You'll need the Cheat Engine 6.4 (that's the program) and then you'll need the CT Trainer file: sw.CT (that's the game configuration file that Cheat Engine uses to enable cheats in the game).
From what I can tell, you need to start the game. Then alt-tab out and start Cheat Engine. Then:
1. open sw.CT and attach it to game process
2. enable script
3. back to game
4. Press Shift+F1 to enable god mode.
Oh, and you can't remove games from your library. You can hide them if you're in manual display mode on your Games Collection list though.
Hope that helps.