Too high AC ? Well don't use that super armor, wear something lighter. Too many rests ? What if you send all food to camp so you don't have enough on you for a full rest ? I didn't try it, but wouldn't you also get the dream scenes on a partial rest ? Don't level up when you can. Fight the goblin camp at Lv 2 and Moonrise Towers at Lv5 if you find those unchallenging. Don't use potions and grenades unless you"re getting hammered and on the verge of losing. Put your party in difficult positions, instead of advantageous ones. It seems to me that you can make any battle as difficult as you want.
Too obvious.
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There are videos out there of people doing Elden Ring naked, with one arm tied behind their back and armed only with a rolled up newspaper.