The secret level you just have to be in the difficulty of the staff, so I have a nightmare staff you just need to have nightmare unlocked.
You only have to gather the items once from there its just huge amounts of gold to upgrade it you can gather it all in normal, the gathering isnt hard mob wise but the random chance of getting the mob/place that has the item AND if it drops is another thing.
The nightmare is equivalent to act 4 nightmare mobs and there are tons of rare mobs. I havent really looked at the xp but the loot stands above any other nightmare gear and atleast the act 1 hell gear partly. The investment is up to you since you can use the staff over and over just pool to a friend and use him. I am upgrading it because the gear farm is good and hell is really hard
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