Silverhawk170485: Talking about action RPGs:
In some action RPGs NPCs have godmode enabled. They can not die. So you can for example lure enemies to NPCs and let the NPCs kill the enemies for you. You just have to watch.
Actually, you don't need the "action" qualifier; this is more a characteristic of WRPGs and WRPG-like games, regardless of whether there are action elements. For example, in Ultima 6, if you can get Lord British to attack an enemy, the enemy will die instantly.
Another example of mine:
In World of Xeen, I like to clear the Dragon Tower at a low level (ideally 14 or less for double XP from enemies). It is necessary to make heavy use of powerful spells like Implosion to reach the item needed to access the tower, but the rewards are great: 20 million XP (nearly 20 levels worth) from books at the top of the tower, some nice amounts of treasure (though opening the chests isn't feasible at this level), and in the Dragon Clouds, I can easily (without fighting any Darkside dragons) reach the fountain that grants +50 temporary levels; this lets me easily train to near level 50 (maybe actually to level 50 if I do it at level 14 or earlier), and then use the fountain to temporarily reach level 100, making the game *much* easier.
Also, in Ys: The Oath in Felghana, after getting the double jump ability, leave the mine and explore the mountains. The enemies will be dangerous, but I level up quickly, can activate some save points, and get a lot of XP (especially from the enemies past the boss that doesn't spawn if you haven't completed the mine). Then I go back to the mine, and the next two bosses are trivial. (I believe this works even on Nightmare mode, though the enemies on the mountain could be quite lethal before you gain a few levels, but those two bosses will still become trivial.)