I like this concept I think it would totally work. My idea for it would be an epic, mostly hopeless quest into some sort of underworld or demonic realm. The forces from that realm are threatening your home so they send in You the strongest most skilled hero of the land, armed with the best equipment that can be found. Your alone perhaps because only one person can enter the portal before it closes, or better yet You, the hero, are cocky, believing you need no one else to accompany you, you can do it yourself.
Once your in there is no turning back, portal closes or by the time you would want to you've gone too far, etc. The first while will be a breeze you cut down your foes easily as warrant of your skills and items, but it all takes it's toll as you progress, your equipment becomes damaged, your food and medical supplies run low, there are no shops around for you to find more equipment, the terrain is hostile with nothing edible or drinkable around, so your equipment deteriorates to nothing, you become hungry, thirsty, injured, thus you become weak, your stats fall, skills and abilities become impossible to do at this state.
You realize your quest is hopeless, but you continue on because that is who you are, a hero. You reach the final boss, a demonic lord, or demi-god of sorts, all powerful. You are weak, hungry, injured, thirsty, little in weapons or armor left. You know it's hopeless your home with succumb to this entity, your family will die, the beautiful green fields will burn. But you fight, it's all you can do now, and by some miracle, perhaps your love for your home, or some colossal amount of luck, you throw down your enemy, your home is safe. Despite the hopelessness, the difficulty, and the hardships, you succeed, you still are a hero....