I intend to make it the most difficult one in category II, as it is actually a byproduct while playing the game, and the only requirement is patience.
it should include obelisks in MB, MDA, LR, GG, labyrinth and perhaps a small part of the East.I'll travel these places again to collect the exact number.
I've traversed most places except the border of the East and Necrovion (and some secret places). I'll exclude some impossible ones.
I remember the period when I could move just one or two steps per day in the East. If the first obelisk is not too deep I prefer counting it in.