For the trophy, you must do the same thing as It wasn’t all a bad dream except you’re beating the game on hell difficulty which is just a harder version of nightmare.
Things to note about hell mode:
Your resistances are lowered by 100.
Enemies have solid immunities to lightning, cold, fire, and magic (but never all at once).
Enemies have a larger health pool than nightmare.
Enemies can be dual or even triple enchanted.
Enemies are more aggressive and hit a lot harder.
You lose a lot more exp than nightmare when you die (you claim a little bit back when you claim your body but not the full amount).
Maps triple in size and orientation.
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