Walkthroughs for custom maps.

To pass the guard, I need a "Mana Amulet" and "Sandglass of Ill Omen"... I can't find the "Mana Amulet" anywhere.

I just checked: The Mana Amulet is located at cell 38,73,0 (hidden behind a demon's secret passage) and is heavily guarded.
You can search in the editor through the menu: Edit - Find or by pressing Ctrl+F (then, if necessary, repeat the search: F3; this way, for example, you can review the location of all tents or monoliths). You just need to know what the object is called in your version of the editor, as the names differ in different translations.